Ink Circuit of an Inking Unit of a Flexographic or Gravure Printing Press

Abstract

The invention relates to an ink circuit of an inking unit of a flexographic or gravure printing press. In order to reduce the changeover costs in relation to the ink circuit of an inking unit of a flexographic or gravure printing press, an ink circuit of an inking unit of a flexographic or gravure printing press is provided, wherein the inking unit has an ink inflow for providing ink which is ready for printing and an ink outflow for transporting away excess ink, wherein the ink inflow is operated by an inflow pump and the ink outflow is operated by an outflow pump, and wherein the outflow pump is a pump which is driven by an electric motor.

Claims

1. An ink circuit of an inking unit of a flexographic or gravure printing press, wherein the inking unit has an ink inflow for providing ink which is ready for printing and an ink outflow for transporting away excess ink, wherein the ink inflow is operated by an inflow pump and the ink outflow is operated by an outflow pump, and wherein the outflow pump is a pump which is driven by an electric motor.

2. The ink circuit according to claim 1, wherein the inflow pump is a pump which is driven by an electric motor.

3. The ink circuit according to claim 1, wherein the pump is an annular piston pump.

4. The ink circuit according to claim 3, wherein a heat exchanger is connected downstream of the annular piston pump, to cool the ink.

5. The ink circuit according to claim 1, wherein the viscosity of the ink conveyed by the pump is determined according to the motor state of the electric motor.

6. The ink circuit according to claim 1, wherein the electric motor is an asynchronous motor.

Description

[0021] Further details and advantages of the invention will be described with reference to the appended drawing, in which:

[0022] FIG. 1 shows the ink circuit according to the present invention.

[0023] The ink circuit 101 according to the present invention is provided for operating an inking unit 102 of a flexographic printing press, wherein the inking unit 102 has an ink inflow 103 for providing ink which is ready for printing and an ink outflow 104 for transporting away excess ink.

[0024] The ink inlet 103 is supplied with ink by the ink reservoir 105 via the pump 106, the pump 106 being an air-driven double diaphragm pump. Valves 107 and 108 enable the ink inflow 103 and thereby also the entire inking unit 102 to be washed with a cleaning agent which is supplied via a point of access 109.

[0025] The ink outflow 104 transports excess ink out of the inking unit 102 via the pump 110, the pump 110 being an annular piston pump which is driven by an asynchronous motor. Such an annular piston pump is known also by the technical term eccentric disc pump and is described in European patent specification EP 0 834 016 B1.

[0026] Since the ink heats up as it passes through the annular piston pump 110, a heat exchanger 111 which cools the ink back down in order to prevent the ink from degrading as a result of excessive heating is provided downstream of the annular piston pump 110. The valves 112 and 113 enable fluid in the outflow to either be returned to the ink reservoir 105 or disposed via line 114.

[0027] A control unit 115 controls all the components of the inking unit, with FIG. 1 showing only the control lines of interest, 116, 117, 118 and 119.

[0028] The asynchronous motor is operated using so-called field-oriented control. A field-oriented control system, also called vector control system, consists of a rotational speed controller based on a secondary current controller. Instantaneous active and reactive current components are controlled. The motor values are saved, or optionally even automatically determined and adapted, in a motor model electronically stored in the converter. This has the advantage that there has to be no separate rotational speed measurement and feedback for controlling rotational speed and torque. Instead, the only value that is fed back for control is the instantaneous current. Based on the level of this current and its phase relation to the voltage, all of the required motor states (rotational speed, slip, torque and even thermal dissipation loss) can be determined.

[0029] Measuring the instantaneous current of the asynchronous motor of the annular piston pump 110 thus allows the torque of the motor and therefore the viscosity of the ink to be accurately determined. When changing printing jobs, this can be used to determine transitions between ink feeding and flow-through of cleaning agent in a simple and accurate manner, thereby also enabling the valves 112 and 113 to be precisely controlled. Overall, this enables the recycling quota of the valuable ink to be optimized and, as a result, changeover costs to be minimized.