Fluid valve, particularly return valve for a painting system

A color changing method for a painting system including an application device for applying a coating agent;

• a color line for feeding coating agent to the application device;
• a main needle valve which is located in the color line upstream before the application device and which selectively releases and blocks off the coating agent;
• a return line for returning at least one of residual coating agent, flushing agent, air, and compressed air during a color change;
• wherein the return line branches off from the color line upstream before the main needle valve or downstream after the main needle valve;
• a return valve which is located in the return line;
• at least one of the return valve and the main needle valve is movable between an opening position in which the fluid valve is at least partially open and a closing position in which the fluid valve is closed, wherein the fluid valve is adjustable between the opening position and the closing position, wherein the fluid valve is configured to be actuated by its own medium, and wherein the fluid valve is configured to switch to the closing position in response to a fluid present on the inlet side, the method comprising:
• painting with a first color paint, wherein the first color is fed over the color line to the application device, and
• flushing at least one of the color line over a return valve into the return line and the application device over the main needle valve, and
• loading the color line with a second color paint, wherein the return valve closes upon actuation by an own medium of the valve if the second color paint is present at the return valve.

A fluid valve with an opening position in which the fluid valve is at least partially open, and a closing position in which the fluid valve is closed, wherein the fluid valve is adjustable between the opening position and the closing position, wherein the fluid valve is configured to be actuated by its own medium, wherein the fluid valve is configured to switch to the closing position in response to a fluid present on the inlet side,

• wherein the fluid valve generates an own medium actuated closing force for switching into the closing position,
• a closing force amplifier configured to amplify the own medium actuated closing force,
• the closing force amplifier includes an amplifier valve,
• the amplifier valve of the closing force amplifier selectively opens and closes a first control air connection which opens into a cylinder and serves for closing the fluid valve,
• the pressure applied to the first control air connection increases the closing force if the amplifier valve is opened,
• the amplifier valve is a sliding valve and comprises a valve slider which is coupled with the piston,
• the valve slider closes the first control air connection if the piston of the fluid valve is in the opening position,
• the valve slider releases the first control air connection if the piston has moved a fraction of its stroke from the opening position in the direction of the closing position so that the force amplification acts.