Method of cleaning a paint feed line of a painting system

1. A method of cleaning a paint feed line of a 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 method comprising:

moving a cleaning substance through the feed line during a cleaning stage between the operational stages; and

filling the feed line with an inert gas at the end of the cleaning stage and 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;

an inert gas source of the inert gas is connected to the second end of the feed line via a first controlled valve;

a collection container is connected to the first end of the feed line though a second controlled valve;

the tank is connected to the first end of the feed line via a third, controlled valve; and

a cleaning substance source of the cleaning substance is connected to the second end of the feed line via a fourth, controlled valve;

said method further comprising:

at the beginning of the cleaning stage, first, opening the first controlled valve to force the residual paint in the feed line, by the inert gas, back into the tank;

then, closing the third valve and opening the second valve;

thereafter, opening the fourth controlled valve to force the cleaning substance though the feed line;

then, closing the fourth valve and allowing the cleaning substance to be removed from the feed line by the inert gas;

thereafter, closing the second valve after the residual cleaning substance has been removed and the feed line has been filled with the inert gas.

2. The method as claimed in claim 1 , further comprising detecting, by a sensor, a boundary between the residual paint and the inert gas.

3. The method as claimed in claim 2 , wherein said second valve is opened and said third valve is closed upon detecting the boundary between the residual paint and the inert gas at a point adjacent the first end of said feed line.

4. The method as claimed in claim 3 , further comprising

detecting, by the same sensor, a boundary between the inert gas and the cleaning substance;

wherein the second valve is closed after a predetermined time period has lapsed after detecting the boundary between the inert gas and the cleaning substance, said predetermined time period being sufficient for the cleaning substance to completely pass the second valve.

5. The method as claimed in claim 1 , comprising releasing, for a predetermined period of time, the cleaning substance from said cleaning substance source into said feed line after the residual paint has cleared the second end of said feed line under the action of the inert gas.

6. The method as claimed in claim 1 , comprising

keeping the second valve open until the cleaning substance has completely passed the second valve, and

after the cleaning substance has completely passed the second valve, closing the first and second valves thereby keeping an amount of the inert gas under pressure within said feed line until the next operational stage begins.

7. The method as claimed in claim 1 , wherein the inert gas is nitrogen.

8. The method as claimed in claim 1 , wherein the cleaning substance is a foam mixture of a cleaning fluid and the inert gas.

9. A method of cleaning a paint feed line of a 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 method comprising:

moving a cleaning substance through the feed line during a cleaning stage between the operational stages;

thereafter, filling the feed line with an inert gas at the end of the cleaning stage;

thereafter, completely closing both ends of said feed line to keep the inert gas under pressure in the feed line until opening of a nozzle of the deposition device, wherein said opening begins the next operational stage, 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;

an inert gas source of the inert gas is connected to the second end of the feed line via a first controlled valve;

a collection container is connected to the first end of the feed line though a second controlled valve;

the tank is connected to the first end of the feed line via a third, controlled valve; and

a cleaning substance source of the cleaning substance is connected to the second end of the feed line via a fourth, controlled valve;

said method further comprising:

at the beginning of the cleaning stage, first, opening the first controlled valve to force the residual paint in the feed line, by the inert gas, back into the tank; and

then, closing the third valve and opening the second valve upon detection of a boundary between the residual paint and the inert gas at a point adjacent the first end of said feed line.

10. The method as claimed in claim 9 , further comprising, after the closing of the third valve and the opening of the second valve,

opening the fourth controlled valve to force the cleaning substance though the feed line;

then, closing the fourth valve and allowing the cleaning substance to be removed from the feed line by the inert gas; and

thereafter, closing the second valve after a predetermined time period has lapsed after detection of a boundary between the inert gas and the cleaning substance, said predetermined time period being sufficient for the cleaning substance to completely pass the second valve.