Dosing system for a coating plant

1. A metering system for a coating installation for coating components, comprising:

an applicator configured to apply the coating material at a discharge quantity metered according to at least one predetermined value,

a first metering device configured to adjust the pressure or the volumetric flow of the coating material applied by the applicator as a function of setpoints which are specified for it by automated installation controls,

a transducer for generating a setpoint which matches the pressure or the volumetric flow of the coating material flowing to the applicator, and

a control device for regulating the metering device as a function of the specified setpoints and of a measurement of the transducer,

wherein a second metering device is connected at the outlet of the first metering device for the coating material flowing to the applicator which, for the precision metering of the applied coating material, regulates its pressure or volumetric flow as a function of the specified setpoints;

wherein the first metering device and the second metering device which serves for fine metering are each controlled by a dedicated control circuit configured to compare a measured value corresponding to the pressure or the volumetric flow of the coating material flowing to the applicator with the at least one predetermined desired value; and

wherein the second metering device includes a piston unit containing a movable piston, by way of whose cylinder chamber adjacent the piston the coating material flows as it is being taken to the applicator, and wherein the piston is configured to be moved by a drive mechanism regulated by the control device to correct the specified pressure or volumetric flow value in the event of deviations from the setpoints.

2. The metering system of claim 1 , wherein at least one of the first metering device and the second metering device for precision metering has its own closed loop control system configured to compares a reading corresponding to the pressure or the volumetric flow of the coating material flowing to the applicator with the specified setpoints.

3. The metering system of claim 1 , wherein the first metering device includes a pressure regulator controlled by the specified setpoints.

4. The metering system of claim 1 , wherein the first metering device includes a volumetric flow regulator controlled by the specified setpoints, the flow regulator having a metering valve as actuator and a controlled electric valve drive.

5. The metering system of claim 1 , wherein the transducer for the first and/or the transducer for the second metering device is a pressure sensor or a flow measurement cell.

6. The metering system of claim 1 , wherein the transducer is a pressure sensor located at the material outlet of the first metering device and/or at the material outlet of the second metering device.

7. The metering system of claim 1 , wherein a flow measurement cell is located as a transducer at the material outlet of the first metering device and/or at the material outlet of the second metering device.

8. The metering system of claim 1 , wherein a pressure sensor configured to measure the material pressure is provided at the material inlet of the applicator.

9. The metering system of claim 1 , wherein a material pressure regulator is positioned upstream of the material inlet of the first metering device, the material pressure regulator configured to automatically adjust a desired feed pressure for the coating material.

10. The metering system of claim 1 , wherein the drive mechanism includes an electric-motor drive.

11. The metering system of claim 1 , wherein the piston unit contains two cylinder chambers separated by the piston in which the piston can be moved, where the coating material flows through the first cylinder chamber in the direction of the applicator and a pressure assisting the piston movement is generated in the second cylinder chamber which is located on the side of the piston opposite the coating material.

12. The metering system of claim 11 , wherein the pressure in the second cylinder chamber can be modified in accordance with the desired direction of motion of the piston.

13. The metering system of claim 1 , wherein during pauses in the coating process in which no material is applied, the coating material taken to the applicator is returned to a material supply device through a circulation loop.

14. The metering system of claim 13 , wherein the piston unit contains two cylinder chambers separated by the piston in which the piston can be moved, where the coating material flows through the first cylinder chamber in the direction of the applicator and a pressure assisting the piston movement is generated in the second cylinder chamber which is located on the side of the piston opposite the coating material; and

wherein the coating material returning through the circulation loop is taken through the second cylinder chamber.

15. The metering system of one of the claim 14 , wherein the assist pressure in the second cylinder chamber is generated at least during application by the material supply pressure in an inlet line leading to the first metering device.

16. The metering system of claim 15 , wherein a switching valve is interposed between the inlet line and the circulation loop with which the inlet line can be selectively connected to the second cylinder chamber.

17. The metering system of claim 1 , wherein the second metering device is formed by a pump with a continuous flow, wherein the pump is configured such that the action of the pump can be reversed and its drive motor can be regulated to correct the pressure or volumetric flow setpoint specified by the first metering device.

18. The metering system of claim 17 , wherein the pump is a gear pump or a rotary piston pump or a screw pump or a piston pump with a piston delivering in both directions.

19. An application robot with a metering system for a coating installation for coating components, comprising:

an applicator configured to apply the coating material at a discharge quantity metered according to at least one predetermined value,

a first metering device configured to adjust the pressure or the volumetric flow of the coating material applied by the applicator as a function of setpoints which are specified for it by automated installation controls,

a transducer for generating a setpoint which matches the pressure or the volumetric flow of the coating material flowing to the applicator, and

a control device for regulating the metering device as a function of the specified setpoints and of a measurement of the transducer,

wherein a second metering device is connected at the outlet of the first metering device for the coating material flowing to the applicator which, for the precision metering of the applied coating material, regulates its pressure or volumetric flow as a function of the specified setpoints,

wherein the second metering device includes a piston unit containing a movable piston, by way of whose cylinder chamber adjacent the piston the coating material flows as it is being taken to the applicator, and wherein the piston is configured to be moved by a drive mechanism regulated by the control device to correct the specified pressure or volumetric flow value in the event of deviations from the setpoints, and

wherein at least the second metering device is located on or in a movable robot member of the application robot.

20. The application robot of claim 19 , wherein the first metering device and the second metering device which serves for fine metering are each controlled by a dedicated control circuit configured to compare a measured value corresponding to the pressure or the volumetric flow of the coating material flowing to the applicator with the at least one predetermined desired value.