During the electrostatic coating with direct charging of an electrically conductive coating material of varying color, it is known to employ an intermediate reservoir for the necessary potential separation between the grounded color changer, which consists of a valve arrangement, and the atomizer, which is placed under high voltage. The reservoir can be filled by the color changer as long as the high voltage on the atomizer has been switched off or the connection line to the atomizer has been emptied, and before the atomizer under high voltage is supplied with material it is first necessary to form an insulated stretch between the reservoir and the color changer, for example, by emptying the supply line of the reservoir i.e. (EP 0 292 778, U.S. Pat. No. 4,932,589, DE 199 37 426, EP 1 314 483 etc.). It is especially expedient for this intermediate reservoir to be configured as a dispensing cylinder for the precisely measured supply of material to the atomizer.
In a painting robot known from WO 2004/037436, the intermediate reservoir is located together with the color changer in the forearm of the robot, consisting of insulation material. In lieu of this, it is also known to arrange dispensing cylinders or a reservoir such as one in the form of a spiral hose joined to a dispensing pump in the atomizer itself, and in the case of dispensing cylinders, the atomizer and/or the dispensing cylinder is interchangeably installed i.e. (EP 0 693 319, EP 0 967 016, EP 1 279 440, EP 1 245 294). On the other hand, as is familiar, dispensing cylinders can also be placed outside of the coating machine, for example, on its outside or on an outer wall of the spray booth i.e. (EP 1 362 642, EP 1 360 996).
Furthermore, from EP 0 796 664 it is known to employ cartridge-like reservoirs configured as dispensing cylinders in the robot arm to supply the paint for painting robots; these are not filled in the robot, but rather after being used they are automatically replaced by new cartridges which have been filled outside. For example, per EP 0 796 665, the cartridges can be connected to a color changer at the external filling station.
If the reservoir is required to be arranged in a movable part of the coating machine, from which it can be removed, it is advisable for it to be taken automatically by the machine itself to a removal station. The removing of a reservoir may be required not only because of the reasons given in the cited EP 0 796 664 and 0 796 665, but also for reasons of maintenance or to replace a faulty reservoir, for example. Moreover, it may be advisable to fill the reservoir in normal operation, and especially for frequently required paint colors, at its operating position within the machine and only to replace it with a different, already filled reservoir in special cases, for example, for special colors. In these situations, with the reservoir arranged in the robot's arm, one has had to be satisfied with the movement capabilities of the latter. While arranging the reservoir in the atomizer provided many more degrees of freedom of motion (axes), this would make the atomizer heavy and bulky, which is detrimental to the movement dynamics, the loading of the axes of the hand joints, and also the accessibility of narrow or hard to reach areas on the work piece, such as interior regions of car bodies.
Another problem in all painting machines of this kind is the wasting of paint and rinse agents which may occur primarily when changing colors in the connection line leading from the reservoir to the atomizer and which will depend on the length of the latter.