Method and apparatus mounted on a painting system to clean a paint feed line

1. An apparatus adapted to be connected to a painting system for cleaning a paint feed line of the painting system in which the paint feed-line connects at least one paint tank to at least one paint deposition device for the purpose of moving the paint during operational stages from the tank to the deposition device, said apparatus comprising a rinsing unit to move a pressurized gas through the feed line during cleaning stages between the operational stages, wherein the rinsing unit comprises

a pressurized inert-gas source; and

means for filling the feed line with said inert gas at the end of a cleaning stage and for keeping the inert gas in the feed line until the next operational stage begins, thereby effectively preventing ambient air from entering the feed line in the time interval between the termination of the cleaning stage and the beginning of the next operational stage;

wherein

said feed line includes first and second opposite ends connected to said tank and said deposition device, respectively;

the inert gas source is adapted to be connected to the second end of the feed line;

the means comprise a first controlled valve coupled to the inert-gas source for connecting the inert-gas source to the feed line;

the rinsing unit further comprises a cleaning-substance source connectable to the second end of the feed line, and a collection container;

said means further comprise a second controlled valve configured such that the first end of the feed line issues through the second controlled valve into the collection container;

said means further comprise a third, controlled valve;

the tank is connectable by the third, controlled valve to the feed line;

said means further comprise a fourth, controlled valve configured such that the feed line is connected at the first end by the fourth controlled valve to at least one further paint tank of the painting system;

the third valve and the fourth valve together define a paint-change unit implementing the selective feeding of paints of different properties from said tanks during the operational stages; and

said means further comprise

a fifth controlled valve coupled to the cleaning substance source for connecting the cleaning substance source to the second end of the feed line; and

controlling means for

following an operational stage, opening the first controlled valve to force the paint in the feed line, by the inert gas, back into the pertinent tank, and

then, closing the third or the fourth valve and opening the second valve, and

thereafter, opening the fifth controlled valve to force the cleaning substance through the feed line, and

then, closing the fifth valve and allowing the cleaning substance to be removed from the feed line, and

thereafter, closing the second valve after the feed line has been filled exclusively with the inert gas.

2. The apparatus as claimed in claim 1 , wherein said controlling means close the first controlled valve no later than the opening of the deposition device initiating the next operational stage.

3. An apparatus adapted to be connected to a painting system, said painting system comprising a paint reservoir, a paint applicator, and a paint feed line having first and second opposite ends connected to said reservoir and said applicator, respectively, for supplying paint from the first end and said reservoir to the second end and said applicator during operational stages, said apparatus being adapted to clean said feed line during cleaning stages between the operational stages, said apparatus comprising an inert gas source connectable to the second end of said feed line for forcing the paint remaining in said feed line after one of the operational stages from the second end to the first end of said feed line;

said apparatus further comprising:

a collection container adapted to be in fluid communication with the first end of said feed line for partially collecting the remaining paint being forced out of the first end of said feed line by said inert gas;

a first controllable valve installable between said inert gas source valve and the second end of said feed line;

a control unit coupled to said first valve and configured to open said first valve to initiate a release of the inert gas from said inert gas source into said feed line at the beginning of the cleaning stage.

a second controllable valve installable between said reservoir and the first end of said feed line; and

a third controllable valve installable between said collection container and the first end of said feed line;

wherein

said control unit is coupled to both said second and third valves and configured to keep the second valve open and the third valve closed for a time interval after the release of the inert gas at the beginning of the cleaning stage, thereby enabling a portion of the remaining paint to return to said reservoir for a subsequent operational stage;

said control unit is further configured to close said second valve and open said third valve when a boundary between the remaining paint and the inert gas has reached a point adjacent the first end of said feed line;

said apparatus further comprises a cleaning substance source connectable to the second end of said feed line;

said control unit is coupled to said cleaning substance source and configured to release, for a predetermined period of time, the cleaning substance from said cleaning substance source into said feed line after the remaining paint has cleared the second end of said feed line under the action of the inert gas;

said apparatus further comprises a sensor for detecting the boundary between the paint and the inert gas; and

said control unit is coupled to said sensor and configured to close said second valve and open said third valve upon receiving from said sensor a signal indicating a detection of the boundary between the paint and the inert gas.

4. The apparatus of claim 3 , wherein

said sensor is further configured to detect a boundary between the cleaning substance and the inert gas; and

said control unit is configured to close the third valve after a predetermined time period has lapsed from receipt, by said control unit, of a signal from said sensor indicating a detection of the boundary between the cleaning substance and the inert gas, said predetermined time period being sufficient for the cleaning substance to completely passed the third valve.