EP1584376B1 - Method for conveying coating material and coating machine - Google Patents

Abstract

The coating application machine such as a painting robot has a supply line (5A, 5B) passing through the robot arm. Residual coating material from the atomizer (3) passes through a pinched hose unit (4A, 4B) to a scraper unit (6), from which it is scraped back into the coating material supply system. The hose is pinched by compressed air passed through a pressure resistant outer hose.

Description

The invention relates to a method for conveying a coating material in a program-controlled multi-axis coating machine with an application device and to such a coating machine for the serial coating of workpieces according to the preamble of the independent patent claims.

The coating machine may in particular be one of the known painting robots, as are customary for the at least predominantly electrostatic exterior and interior painting of workpieces such as vehicle bodies or, for example, in the automobile supplier industry and their attachments ( JOT 1/2004, p. 12-13 ).

Typical in industrial paint shops for such and similar purposes frequent color changes during production and the necessary before supplying the application device with the new color measures for emptying and cleaning the paint lines. Since the remaining before a color change in the line paint is not simply rinsed and thus discarded, which is hardly accepted in modern systems, he is usually pushed back for reuse in the associated ring lines or reservoir of the paint supply system. For pushing back the paint has been proven for some years, the pigging technique, which has the very significant advantage that the color of the moving through the paint tubes new scraper virtually completely stripped from the tube walls and removed from the hoses. For this reason, should be piggable Up to now, hoses have been laid as far as possible into the atomizer used as an application device, and the remaining colored lake has even been molten back from the paint nozzle ( JOT 3/2004; Pp. 22-24 ; EP 1 314 480 ). The degree of reuse remaining paint residues determines the efficiency of the supply system.

In addition, pigs not only serve to push back color paint during a color change, but also to supply the coating material to the atomizer before or during a coating operation or to convey washing agent through the system and, if necessary, to the atomizer or from the latter in the reverse direction ( EP 1 270 083 . EP 1 362 641 . EP 1 362 642 ).

If the foremost pigging stations in the direction of supply are located in the atomiser of a painting robot, the relevant piggable tubes must be routed through the wrist, see the generic type DE 102 23 498 , The wrists of modern painting robots are indeed designed so hollow that leading to the atomizer hose and other lines and per se also pig pipes can be passed through their interior ( US 4,708,580 ). In practice, however, problems arise in particular if more than just a piggable tube is to be laid through the joint and if these tubes should also be designed high-voltage resistant, as may be required for example in the direct charging of water paint in electrostatic atomizers. Such hoses ( DE 102 39 516 ) can only be produced with a relatively large diameter, whereby it must also be taken into account that too small inner diameters lead to undesirably high pressure losses. The relatively thick tubes are correspondingly stiff and less flexible, so that they are poorly bendable within the joints.

In addition, in the joint movements of the required for the unhindered passage of the pigs bending radius of the molded hoses must not be fallen below. Because of these requirements, the piggability of the supply lines to the atomizer was possibly feasible with large-volume joint constructions of the coating machine. This is true not only for robots, but also for the joints of other multi-axis coating machines such as roof and side machines, but especially in painting robots large-volume wrists are undesirable because they affect not only the dynamics of movement, but especially the accessibility of possibly narrow interiors and other Can obstruct areas of workpieces.

From the WO 03/086671 A1 For example, a method for pushing back the color coat remaining in the supply line of a painting device during a color change is already known, in which the line is emptied by deformation similar to the known peristaltic pump principle. For this purpose, a relatively soft inner tube is used as the supply line, which is surrounded by a pressure-resistant outer tube, and passed into the gap between the inner and outer tubes compressed air or another pressure medium, which acts on the outer circumference of the inner tube. For example, if the hose assembly connects a nebulizer to a color change valve assembly, compressed air is passed between outer jacket and inner tube during color change on the nebulizer side, and since the jacket does not yield, the inner tube is compressed from the nebulizer to the color changer and thereby the residual paint of the supply tube into the nipple Supply system returned. The stated aim of the known method is to avoid brittle lines. This process, also known as "squeeze-out", is the pigging technique but in different inferior. On the one hand, it is hardly possible in practice to completely compress the inner tube during squeezing, so that there is always a certain residue of paint remaining, which is then rinsed out, for which comparatively large amounts of detergent are required. In addition, the inner tube is prone to elongation due to the bruising repeated with each color change. For these reasons, such tube systems are relatively poor for painting robots and other coating machines in which long tubes of, for example, more than 20 m are required.

Starting from the above-discussed known painting robots or other machines with built-in gemold lines, the invention has for its object to provide a method or a coating machine with a gememchten within the machine line with which on the one hand largely the main advantage of the pig technology can be used, namely the almost complete emptying of the gemoldten line, while on the other hand, at least in the vicinity of the coating device no bulky joint with large interiors is necessary.

This object is solved by the features of the claims.

The invention is based on the finding that all the above-described problems can be solved in a nearly perfect manner, if the proven pigging technology is meaningfully combined with the per se known hose crimping method. If you place the pig target station in the coating machine such as in a robotic arm as close to the atomizer, but still in front of a joint such as the robot's hand axis undesirable narrow for the pigging technology Interior, can be used between the supply system and this destination unrestricted all advantages of pig technology such as low detergent consumption and high efficiency of paint recovery even with long hoses. In the remaining connection path between the pig destination station and the application device, however, the advantages of Quetschmethode come into play, namely the possibility to pass the tubes with relatively small diameters and small bending radii through the robot wrist or other joints of coating machines, with high packing density for the hose package used and long life of the hoses can be achieved. Unaffected by the change in the tube emptying method within the coating machine, the possibility remains of providing the evacuated line for the potential separation between the atomizer and the grounded supply system required in the electrostatic coating with water-based paint and other conductive media.

The inventively by the use of squeeze hose systems instead of gemold connecting lines in a machine joint achievable reduction in space requirements is based not only on the type of hoses used, but also on a possible reduction in the number of required hoses. In the pigging technology additional hoses or control lines for various valve functions of the pig downstream of the joint are required in addition to the actual color hoses, which must also be performed by the joint and omitted in the crushing technique.

For example, since voluminous joint structures are no longer required for the hand axis of painting robots, because no pigging hoses need to be passed through and yet the desired color recovery is easily possible, slim robots can be realized with good, at least in the hand axis not impaired by pig hoses movement dynamics. Such robots are particularly suitable for the coating of narrow interiors and workpieces with small pitches.

The mentioned principal disadvantages of Schlauchquetschmethode compared to the pigging play in the invention because of the small length of the tubes between the application device and the pig destination station is not an essential role, in particular, the recovery efficiency is only slightly reduced.

Although the method described herein is particularly applicable to repressing the residual color remaining before a color change in the supply lines to the atomizer, the described advantages of the invention may also be important in the evacuation of hoses in the direction of the atomizer.

On the embodiment shown in the drawing, the invention will be explained in more detail. The drawing shows schematically and greatly simplifies the cable entry through the wrist of a painting robot.

As shown, a hollow three-axis wrist 2 is attached to the robot arm 1, to which an electrostatic rotary atomizer 3 is flanged. Such constructions are known and customary and therefore require no further description. In a likewise known manner lead through the wrist 2 two flexible and according to the wrist movements bendable lines 4A and 4B for ink supply of the atomizer in A / B operation, the well-known allows a time-saving color change. By eliminating the time gained by A / B operation with two parallel lines, a single line 4 would suffice.

For the ink supply of the atomizer 3 are further used, for example, two ummchte supply lines 5A and 5B, which are performed by a remote (not shown) color change valve assembly through the arm 1 to a arm end arranged at the pig station 6 and in particular from multi-layered hoses in the DE 102 39 516 described type can exist. The color-changing valve assembly is in turn connected to a supply system located at least partially outside the coating machine, which may include ring loops leading to the color changer. To connect the umholchten supply lines 5A and 5B with the leading through the wrist 2 lines 4A and 4B, a control valve assembly 7 is shown only schematically or in the pig station 6 is provided.

According to the invention, the connection lines 4A and 4B leading from the pig station 6 to the atomizer 3 each consist of a squeeze hose system in the WO 03/086671 A1 described type, ie from a soft elastic, radially compressible inner tube and the inner tube in the idle state preferably tightly fitting pressure-tight jacket tube. As shown enlarged in the detail view X, between the jacket tube 41 and the inner tube 42 through a opening at the interface between them channel 10, which is connected at its opposite end via a controlled valve 11 to a pressure line 12, a pressure medium such as Compressed air to be passed. The channel 10 and the valve 11 may be located within the atomizer 3 or at its mounting flange. Due to the nature of the tubes 41 and 42 is compressed by the pressure medium, the inner tube 42 to its emptying in the known manner, wherein the pressure medium at the opposite end of the respective line 4A can be removed by a further controlled valve 14. The pressure of the pressure medium is sufficiently higher than the pressure prevailing in the line system lacquer pressure against which the remaining paint in the tube 42 is to be pushed back. In an expedient embodiment, the inner tube 42 of an elastomeric plastic such as TPU (thermoplastic polyurethanes) and the jacket tube made of a plastic such as PA (polyamide) or FEP (fluorinated ethylene propylene) exist. When choosing the material for the inner tube, it should be taken into account, inter alia, that it should be compressible up to a passage cross-section of almost zero that can withstand considerable mechanical stress without elongation or other damage over a long period of operation and also possibly resistant to a solvent used ,

In operation, to supply the atomizer 3 Farblack can be promoted in a known manner by the mentioned color change valve arrangement forth through the umgelchte supply line 5A and the connecting line 4A to the atomizer, for example using a piston meter or other metering pump. If a color change is required after completion of the coating operation, the connection between the atomizer-side end of the conduit 4A and the atomizer is blocked and the colored paint left in the conduit 4A by introducing the pressure medium through the valve 11 opened for this purpose and the resulting squeezing of the inner tube 42 pushed back in the known manner to the pig station 6, from where he then from a pig waiting there through the supply line 5A back to a loop or container of the paint supply system. After the squeezing the inner tube 42 in the in the WO 03/086671 A1 be rinsed described manner, which is possible both from the atomizer ago and from the pig station 6 ago. Instead, but considering the brevity of practically only by the wrist 2 extending line 4A and the corresponding small amount of remaining after squeezing paint residue is conceivable to dispense with the subsequent rinsing and later pass through another color without further notice. During the emptying of the line 4A in the direction of the pig station 6, a new color towards the atomizer can already be conveyed by the second line 4B parallel to it, after which also the paint remaining in this line is pushed back into the pig station 6 in the manner described ,

Already when laying only a single paint line through the wrist 2, the invention has the above-mentioned significant advantages. In the described preferred embodiment of an A / B system, however, the achievable according to the invention reduction of space requirements is particularly clear. If one considers the representation of the wrist 2 with the lines 4A and 4B as approximately true to scale, would be required for a gemoltes connection system hose package of paint and control lines almost fill the entire interior of the same wrist, so that the required mobility would not be guaranteed and the Wrist 2 would have to be replaced by a larger, so unwanted bulky construction.

Claims (9)

1. A method of conveying a coating material in a program controlled multiple axis coating machine with an applicator (3), in which the coating material is supplied to the applicator (3) through at least one pigged supply line (5A,5B) within the coating machine, which is connected to a supply system, and in which the coating material is conveyed through a connecting conduit (4A,4B), which passes through the interior of a joint construction (2) of the coating machine between the pigged supply line (5A,5B) and the applicator (3), characterised in that the coating material is conveyed through the joint construction (2) by deformation of a hose (42) of the connecting line (4A,4B), whose periphery is acted on by a pressure medium, wherein the coating material remaining in the connecting line (4A,4B) after a coating process is forced back into the pigged supply line (5A,5B) by deformation of the connecting line or the connecting line (4A,4B) is emptied in the direction towards the applicator (3).
2. A method as claimed in claim 1, characterised in that the outer periphery of an inner hose (42) of the connecting line (4A) is acted on, in order to deform it, by a pressure medium, which is conducted between the inner hose (42) and a sheath (41) coaxially surrounding the inner hose (42).
3. A method as claimed in one of claims 1 to 2, characterised in that the coating material is forced back by deformation of the connecting line (4A,4B) of the coating device (3) through a wrist joint (2) of the coating machine, on which the coating device (3) is mounted, to a pig station (6) which is located on the side of wrist joint (2) in the vicinity of the coating device (3) remote from the coating device (3) in or on an arm (1) of the coating machine.
4. A method as claimed in one of claims 1 to 3, characterised in that the coating material remaining in the connecting line (4A,4B) is forced back after each colour change of the coating material.
5. A method as claimed in one of claims 1 to 4, characterised in that coating material remaining in a first connecting line (4A) is forced back in the direction towards the pigged supply line (5A) whilst another coating material is conveyed through a second connecting line (4B) extending through the joint construction (2) parallel to the first connecting line (4A) in the direction towards the applicator (3).
6. A program controlled multiple axis coating machine, particularly a robot, for an applicator (3) for the serial coating of workpieces with at least one pigged supply line (5A,5B) extending in an arm (1) of the coating machine and with a connecting line (4A,4B) extending through the interior of a joint construction (2) of the coating machine from the supply line to the coating device (3), characterised in that a device (11,14) is provided, with which a hose (42) of the connecting line (4A,4B) is deformable by the application to its outer periphery of a pressure medium and that as a result of the deformation in this region between the applicator (3) and a pig station (6) located on the side of the joint construction (2) remote from the applicator, coating material situated in the connecting line (4A,4B) may be forced out of the latter into the pigged supply line or may be emptied in the direction towards the applicator.
7. A coating machine as claimed in claim 6, characterised in that the deformable connecting line (4A,4B) passes through a, in particular multiple axis, wrist joint (2) of the coating machine, on which the coating device (3) is mounted, and is connected on the side of the wrist joint (2) remote from the coating device, in its vicinity, to the pig station (6), which is arranged in an arm (1) of the coating machine, of the pigged supply line (5A,5B).
8. A coating machine as claimed in claim 6 or 7, characterised in that within the joint construction (2), an inner hose (42) of the connecting line (4A,4B) is coaxially surrounded by a tubular or hose-shaped sheath (41), into which the pressurised medium is conducted for pressure draining the connecting line (4A,4B), wherein the inner hose (42) and the sheath (41) are so constructed that when pressure is applied only the inner hose (42) deflects.
9. A coating machine as claimed in one of claims 6 to 8, characterised in that two connecting lines (4A,4B), which may be emptied by their deformation, extend parallel to one another through the joint construction (2).

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