Patent Publication Number: US-6908048-B2

Title: Device for supplying a powdery coating product to a sprayer and spray installation comprising same

Description:
The invention relates to a device for supplying powdery coating product to a sprayer and to an installation for spraying powdery coating product comprising, inter alia, such a device. 
     In the domain of installations for spraying powdery coating product, it is known to supply each sprayer of an installation with a mixture of coating product and a conveyance gas which is most often air. In certain installations, a sprayer must be supplied with a plurality of types of coating product which are used selectively, as a function of the nature of the coating to be produced. For example, in the case of an installation for spraying coating product on automobile vehicle bodies, it is necessary to provide painting each body in the colour chosen by the customer. 
     By FR-A-2 441 435, it is known to cause lines connected to different reservoirs of powdery product to converge towards a dispenser in which they are arranged as a cone. The spatial distribution and the number of these lines are imposed by the geometry of the dispenser. It is thus necessary to provide different types of dispenser as a function of the number of coating products having to supply the sprayer. In addition, complex systems for cleaning the different pipes and dispensers must be provided. 
     This device presents such dimensions that it must necessarily be placed at a distance from the sprayer that it supplies, with the result that the pipe connecting the dispenser to the sprayer must be cleaned, whenever the product is changed, over a relatively long distance, this increasing the quantities of product wasted and the time for changing the product. 
     JP-A-55-022 355 furthermore discloses a one-piece manifold into which open out coating product supply conduits. This common manifold cannot develop as a function of the number of conduits to be connected. The same applies to the mixture known from U.S. Pat. No. 3,912,235 which comes under the technical domain of thermal projection. 
     It is more particularly these drawbacks that the invention intends to overcome by proposing a supply device which makes it possible to supply a sprayer with at least two types of powdery coating product, this device being easily adaptable to the number of products to be used and being able to be easily exchanged. 
     In this spirit, the invention concerns a device for supplying a sprayer with a powdery coating product, this device comprising at least two modules each connected to a source of coating product and each forming a part of the principal channel of a common manifold connected to the sprayer for circulating the product. 
     Thanks to the invention, the modular structure of the device of the invention makes it possible to adapt the number of modules used to the number of different sources of coating product, the common manifold being created, as additional modules are added, by the modules themselves. The modular structure of the device of the invention makes it possible to give it relatively small dimensions allowing it to be implanted as close as possible to a sprayer, particularly at the level of an arm of a robot displacing the sprayer opposite the objects to be coated. The length of pipe having to be cleaned downstream of this device, whenever coating product is changed, is short, which is advantageous in terms of quantity of product wasted and the time for changing product. 
     According to advantageous but non-obligatory aspects of the invention, the device incorporates one or more of the following characteristics:
         it comprises a cleaning module connected to a source of cleaning fluid and forming an upstream part of the common manifold.   each module comprises at least one valve adapted to place an inlet of the module, connected to the source of product or of cleaning fluid, and the manifold, selectively in communication. Such a valve makes it possible to control each module so that it delivers, or not, coating product or cleaning fluid to the common manifold and that it thus supplies, or not, the sprayer.   each module comprises a conduit connecting an inlet of the module to the part of the manifold formed by this module while the manifold formed by the different modules extends in a first direction and the conduit of each module extends in a second direction, the angle between these directions, taken in the direction of flow of the product in this conduit and this manifold, being an acute angle. This geometry of the modules allows an easy transition of the flow of the mixture of entraining gas and of coating product between the conduit and the part of the manifold formed in each module.   the modules are assembled in reversible manner, their number being able to be adapted to the number of sources of coating product to which the sprayer must be connected.   each module comprises a base element in which is formed the part of the manifold and a zone of join of the manifold with a conduit. Each module also comprises a connection element defining the inlet of the conduit and a valve for controlling the flow of the product in the conduit, this valve being disposed between the base element and the connection element. Each module is thus formed by two essential elements and by a valve captive between these elements and protected thereby from the outside.       

     According to an advantageous form of embodiment of the invention, at least one of the modules forms a first supply conduit of the manifold and a second supply conduit of a channel for recirculation of the coating product, these first and second conduits extending from a common inlet of the module. In this embodiment, a circulation of the mixture of entraining gas and of powdery coating product may be permanently maintained up to each module, the mixture of air and of powder being directed either towards the supply manifold of the sprayer or towards the channel for recirculation. This avoids the transient states of placing the powder in movement as well as the cleaning of the supply conduits of each module. This embodiment is therefore particularly advantageous concerning the time for changing coating product and the minimization of the quantities of product wasted during a change. In that case, it may be provided that the first and second conduits each be equipped with a controlled valve adapted to allow and/or interrupt flow of the coating product in the conduit in question. 
     The valves used are advantageously sleeve type valves which present the particular advantage of operating without impediment in a relatively aggressive environment, i.e. in contact with a mixture of air and of powder. 
     The invention also relates to an installation for spraying powdery coating product which comprises at least one sprayer supplied by a device such as described hereinabove. Such an installation is economical to manufacture, due to the modular nature of the device, and to exploit, due to the minimization of the quantities of coating product wasted and of the rapid time for changing shade. Such an installation is easily adapted to the variations of its conditions of use, particularly to the number of coating products capable of supplying each sprayer. 
    
    
     
       The invention will be more readily understood and other advantages thereof will appear more clearly in the light of the following description of two coating product supply devices integrated in a spraying installation in accordance with its principle, given solely by way of example and made with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view, with parts torn away, of an installation for spraying coating product in accordance with a first form of embodiment of the invention. 
         FIG. 2  is an exploded view in perspective, with a constituent module of the supply device used in the installation of  FIG. 1 , torn away. 
         FIG. 3  is an exploded view in perspective of a sleeve valve used in the module of FIG.  2 . 
         FIG. 4  is a side view of the supply device used in the installation of FIG.  1 . 
         FIG. 5  is a view similar to  FIG. 1  for an installation in accordance with a second form of embodiment of the invention, and 
         FIG. 6  is a side view of the supply device used in the installation of FIG.  5 . 
     
    
    
     The installation shown in  FIG. 1  comprises a sprayer  1  of manual type intended to spray a cloud  2  of a mixture of entraining gas and of powdery coating product onto objects  3  to be coated. The sprayer  1  is of electrostatic type and is connected to a high-voltage unit  4  thanks to a conducting cable  5 . 
     The sprayer  1  is also supplied with a mixture of entraining gas and of powdery coating product thanks to a flexible pipe  6  connected to a device  10  for supplying it selectively with a product from among four products P 1 , P 2 , P 3  and P 4  respectively contained in four vats B 1 , B 2 , B 3  and B 4  and pumped thanks to Venturi effect suction systems V 1 , V 2 , V 3 , V 4 . The device  10  is connected to each Venturi V 1  to V 4  by a pipe T 1  to T 4 . 
     The device  10  comprises four modules  11 ,  12 ,  13 ,  14 , modules  11  and  12  being shown in  FIG. 1  with a half torn away, while module  13  is shown with a quarter torn away and module  14  is shown without any parts torn away. The device  10  comprises a fifth module  15  connected to a source of pressurized air S by a pipe T 5 . The device  10  also comprises a head  16  from which extends a connection element  16   a  intended to cooperate with the pipe  6 . 
     X-X′ denotes the axis of symmetry of the element  16   a . The modules  11  to  15  and the head  16  are juxtaposed along axis X-X′. 
     The module  11  comprises a base element  111  in which is formed a channel  112  which extends, when the device  10  is in mounted configuration, in the direction of axis X-X′, passing right through the element  111 . 
     The module  11  also comprises a second element  113  bearing a element  113   a  for connection with pipe T 1 . The interior volume of the element  113  defines, with element  111 , a conduit  114  of substantially cylindrical shape and of which Y-Y′ denotes the central axis. The conduit  114  extends in element  111  up to a zone of join  115  with the channel  112 . In other words, the conduit  114  opens out into the channel  112  at the level of zone  115 . 
       114 A denotes the upstream part of the conduit  114  formed the element  113  and  114 B its downstream part formed in the element  111  and terminate in zone  115 . A sleeve valve  116  is arranged in the conduit  114 , in both parts  114 A and  114 B. In fact, the valve  116  is arranged between elements  111  and  113 . 
     The structure of the valve  116  is more particularly visible in FIG.  3 . This valve comprises a tubular element  116 A pierced with two radial orifices  116 B and inside which is arranged an elastic sleeve  116 C maintained in place in the element  116 A thanks to two rings  116 D. When a circulation of air is to occur in conduit  114 , the sleeve  116 C remains applied against the inner surface of the element  116 . When the circulation in the conduit  114  is to be interrupted, a control air pressure is applied on the sleeve  116 C through the orifices  116 B, as represented by arrow F 1  in  FIG. 1 , which has the effect of pinching the sleeve  116 C and of thus cutting the flow in the conduit  114 . An orifice  113   b  visible in  FIG. 4  is provided in the element  113  for the admission of control air up to the valve  116 . 
     The modules  12 ,  13  and  14  are identical to the module  11  and each formed by a base element  121 ,  131  or  141  and by a connection element  123 ,  133  or  143 . Each module  12 ,  13  and  14  also comprises a sleeve valve  126 ,  136  or  146 . 
     The element  121  defines a channel  122  which is substantially aligned with the channel  112 , along axis X-X′, when the device  10  is in mounted configuration. In the same way, the modules  13  and  14  each define a channel  132 ,  142  likewise aligned on axis X-X′ and with an axial passage  162  of the head  16 . The elements  112 ,  122 ,  132 ,  142  and  162  thus form a manifold C through which may circulate an air/powder mixture coming from one of the pipes T 1  to T 4  through the conduit  114  or one of the equivalent conduits  124 ,  134  or  144  of the modules  12 ,  13  and  14 . 
     The module  15  also defines a conduit  154  which opens out in a channel  152  aligned with the channel  142  of the module  14  when the device is in mounted configuration. The module  15  is also equipped with a sleeve valve  156  making it possible to open or to close the conduit  154 . 
     When the valve  156  of the module  15  is open, while valves  116 ,  126 ,  136  and  146  are closed, air flows from the source S in the direction of the sprayer  1 , successively traversing the channels  152 ,  142 ,  132 ,  122 ,  112  and the passage  162 , as well as the element  16 A and the pipe  6 . This makes it possible to clean the device  10 , the pipe  6  and the sprayer  1  in particularly simple and rapid manner. 
     The elements  11  to  16  are maintained in the form of a mechanical unit thanks to two threaded rods  17  and  17 ′ which pass through the base elements  111  and equivalent and the base element  151  of the module  15  as well as the head  16 . 
     The head  16  and the module  15  are likewise each provided with two screws  18  allowing the element  10  to be mounted on a plate (not shown). 
     The modular nature of the device  10  makes it possible to adapt the number of modules  11  or equivalent to the number of coating products having to be supplied to the sprayer  1 . For example, if an additional coating is to be used in the installation of  FIGS. 1  to  4 , it suffices to insert between the module  11  and the head  16  a module identical to module  11  and to change the rods  17  and  17 ′ to use rods of suitable length. The fact that each module  11  or equivalent constitutes a part of the common manifold C therefore makes it possible to permanently adapt the length of this manifold to the effective number of modules used. 
     Arrow F 2  represents the flow of a mixture of entraining gas and of coating product in the conduit  114 . Arrow F 3  represents the flow of coating product in the channel  112 . Arrow F 2  is disposed in direction Y-Y′ and oriented towards the channel  112  while arrow F 3  is disposed in the direction of axis X-X′ and towards the head  116 . The angle α between the directions of arrows F 2  and F 3  is of the order of 45°, with the result that the change of direction of the flow in the zone  115  is not too sudden, this avoiding an accumulation of powder in this zone and a possible “rise” of the mixture towards the modules  12  and following. 
     In practice, two possibilities may be considered, the angle α varying from 20° to 90°.
         for powders which are relatively easy to transport in an air flow, the smaller the angle α is, the more the pressure drops at the level of zone  115  are slight. The angle α is chosen between 20 and 45°, the value of 20° being a minimum for a reason of mechanical design, while the value of 45° corresponds to a maximum inclination for a smooth flow. The flowrate of powder used may in that case be great.   for powders which are relatively difficult to transport, the agglomerates formed by fusion of the powder in the zone  115  should be avoided. To that end, the speed of the air/powder mixture and the disturbances generated by a pronounced angle α, for example included between 45° and 90°, is privileged. Such an angle prevents the powder from being deposited in zone  115 . In an unfavourable case where a slight deposit is formed, it would be evacuated by the air/powder mixture arriving thereafter. The choice of the values of the angle α is then made to the detriment of the maximum flowrate and may generate rises of powder towards the upstream of the manifold C.       

     In the second form of embodiment of the invention shown in  FIGS. 5 and 6 , the elements similar to those of the first embodiment bear identical references increased by 200. 
     The sprayer  201  of this form of embodiment is an automatic sprayer supported by the arm  207  of a robot. A device  210  is provided for supply of the sprayer  201  from two vats B 1 , B 2  each containing a coating product P 1 , P 2  respectively, and equipped with a Venturi entrainment system V 1 , V 2  respectively. 
     The device  210  comprises a first module  211  represented with a half torn away and a module  212  shown in an outside view, as well as a cleaning module  215  connected to a pressurized air source S. 
     The modules  211  and  212  are respectively connected by a pipe T 1 , T 2  to the Venturi devices V 1  and V 2 , while module  215  is connected to a source S of pressurized air by a pipe T 5 . 
     The module  211  comprises a base element  2111  in which is formed a channel  2112  extending essentially in the direction of an axis X-X′. The base element  2121  of the module  212  also defines a channel  2122  which is aligned with the channel  2112  when the device is in mounted configuration. As for the cleaning module  2115 , it defines an end part  2152  of channel in its base element  2151 . A head  216  constitutes the downstream part of the device  210  and is provided with a passage  2162  which is aligned with the channnels  2112 ,  2122  and  2152 , thus forming a manifold C for the coating product coming from a conduit  2114  of the module  211 , or from a conduit  2124  of the module  212 . 
     The cleaning module  215  is also provided with a conduit  2154  for injecting cleaning air coming from the source S in the upstream part  2152  of the manifold C. 
     Each conduit  2114  or  2124  is equipped with a sleeve valve  2116  or  2126 . 
     As previously, the valve  2116  is controlled by injection of air, as represented by arrow F 1  in FIG.  5 . 
     Parallel to conduit  2114 , a conduit  2117  extends, from the inlet  2113   a  of a connection element  2113  of the module  211  up to in the base element  2111 . This channel comprises an upstream part  2117 A formed in the element  2113  and a downstream part  2117 B formed in the element  2111 , a sleeve valve  2118  being housed in this conduit, between elements  2111  and  2113 . 
     The downstream part of the conduit  2117  is bent by about 90°, with the result that it makes it possible to supply a connection element  2111   a  connected to the vat B 1  by a pipe T′ 1  for recirculation. The conduit  2117  might also be bent by an obtuse angle, the choice of the value of this angle being able to be made as a function of the nature of the powder, as indicated hereinabove with reference to angle α. 
       2113   b  denotes the conduit in which the control air is injected around the supple part of the sleeve valve  2116 , as represented by arrow F 1 .  2113 ′ b  denotes the channel, likewise formed in the element  2113 , through which the control air is injected around the sleeve valve  2118 , as represented by arrow F′ 1 . 
     Operation is as follows: From a branching  2113   c  between the conduits  2114  and  2117 , the mixture of air and of entraining gas coming from the vat B 1  through the pipe T 1  is directed either towards the channel C, through the conduit  2114  and the valve  2116 , or towards the recirculation pipe T′ 1  through the channel  2117 , the valve  2118  and the connection element  2111   a.    
     The sleeve valves  2116  and  2118  are piloted, as represented by arrows F 1  and F′ 1 , to be opened and closed in phase opposition, one of these valves being open when the other is closed. Coating product may circulate permanently in the pipe T 1 , being directed either towards the manifold C, or towards the pipe T′ 1 . In this way, when it is necessary to use a new product P 1  or P 2 , no transitory phase of moving the mixture of entraining gas/product has to be provided, the time for changing coating product between the products P 1  and P 2  thus being very rapid. 
     The second module  212  is made in the same manner and makes it possible to cause the coating product P 2  to be recirculated in the direction of the vat B 2  thanks to a pipe T′ 2 . 
     Likewise as previously, the modules  211  and  212  are assembled in reversible manner thanks to threaded rods  217  and  217 ′. It is thus possible to adapt the number of modules of the device  210  to the number of coating products to be used. 
     The module  210  is particularly compact and, in this respect, it may be mounted on the arm  207  of the robot supporting the sprayer  201 . In this way, the length of the pipe  206  connecting the device  210  to the sprayer  201  may be minimized, which makes it possible likewise to minimize the quantities of coating product wasted during a change of product, these quantities corresponding approximately to the quantity of coating product located in the manifold C and in the conduit  206 . The small volume of the pipe  206  also facilitates rapid cleaning thereof. 
     A mixed installation with one or more modules of the type of module  11  and one or more modules of the type of module  211  may be envisaged, in the same way as an association of modules whose conduits have different angles of inclination α with respect to the principal direction of the manifold C.