Powder conveying device for coating powder and powder coating system comprising a powder conveying device

1. A powder conveying device for coating powder, comprising:

a powder conveyor having a powder inlet and a powder outlet duct through which coating powder is conveyable,

a powder outlet valve located in the powder outlet duct, the powder outlet valve being configured to open or close the powder outlet duct for permitting or restricting conveyance of the coating powder therethrough,

a setpoint value generator configured to specify a setpoint opening period of the powder outlet valve,

a sensor configured to determine an actual opening period of the powder outlet valve by detecting the movement of powder in the outlet duct downstream of the outlet valve,

an evaluation unit configured to: (i) receive the setpoint opening period from the setpoint value generator, (ii) receive the actual opening period from the sensor, and (iii) determine the deviation between the setpoint opening period and the actual opening period, and

a controller configured to receive a signal from the evaluation unit corresponding with the deviation, and being configured to control the powder outlet valve in response to the signal for minimizing the deviation between the setpoint opening period and the actual opening period.

2. The powder conveying device according to claim 1 , wherein the sensor is mounted in or on the outlet duct downstream of the outlet valve, and is embodied as influence sensor.

3. The powder conveying device according to claim 1 , wherein the sensor is mounted on the outlet duct downstream of the outlet valve, and is embodied as optical sensor or as density sensor or as microwave sensor.

4. The powder conveying device according to claim 1 ,

wherein the powder conveyor has a further powder outlet duct,

wherein a further powder outlet valve for opening or for closing the further powder outlet duct is provided, and

wherein a further sensor for determining the actual opening period of the further powder outlet valve is provided.

5. The powder conveying device according to claim 4 , wherein the evaluation unit is also provided to determine the deviation between the setpoint opening period of the further powder outlet valve and the actual opening period of the further powder outlet valve.

6. The powder conveying device according to claim 4 , wherein a further setpoint value generator for specify a setpoint opening period of the further powder outlet valve is provided.

7. The powder conveying device according to claim 4 , wherein the evaluation unit is additionally provided to compare the actual opening period of the powder outlet valve to the actual opening period of the further powder outlet valve.

8. The powder conveying device according to claim 1 , wherein the powder conveyor has a powder working container, which can be pressurized.

9. The powder conveying device according to claim 1 , wherein the powder conveyor comprises an injector.

10. The powder conveying device according to claim 1 , wherein the powder conveyor comprises a dense flow feed pump.

11. The powder conveying device according to claim 1 , wherein the powder outlet valve is embodied as tube squeezer.

12. A powder coating system comprising the powder conveying device according to claim 1 , wherein a powder applicator, which is connected to the outlet duct of the powder conveying device via a powder line.

13. The powder coating system according to claim 12 , wherein the powder applicator is a spray applicator having a spray outlet that opens to an external environment, the spray applicator being configured to spray the powder through the spray outlet into the external environment.

14. The powder coating system according to claim 13 , further comprising a pressurizable powder working container configured to contain coating powder under pneumatic pressure, the powder working container having a powder inlet and the outlet duct through which coating powder is conveyable under pneumatic pressure.