BR-112021011479-B1 - INK DISTRIBUTION SYSTEM AND ROTARY PRINTING UNIT

BR112021011479B1BR 112021011479 B1BR112021011479 B1BR 112021011479B1BR-112021011479-B1

Abstract

SYSTEM AND METHOD FOR DISTRIBUTING INK USING PRESSURE. The present invention relates to a system for distributing a precise and continuous quantity of ink to a large printing machine. The distribution system can be judiciously combined into a more elaborate distribution system that uses two chambers with ink having different densities to distribute ink with a precise, adjustable, and stable ink density. The distribution system can be used to compensate for deviations in quality observed in presses when speed or any environmental parameters vary.

Inventors

Federico D'Annunzio
ANTONIO BELLOSI
Andrea Melchiorri

Assignees

BOBST FIRENZE S.R.L

Dates

Publication Date: 20260310
Application Date: 20191218
Priority Date: 20181220

Claims (10)

1. Ink distribution system (1), comprising: a first chamber (2) configured to hold ink (5) under pressure; a first ink channel (3) connecting an outlet (13) of the first chamber to an outlet (14) of an ink distribution system; a first pressure source (4) configured to send air with adjustable pressure to the first chamber (2); a control system (100) functionally connected to the first pressure source (4) and to a first sensor (6); characterized in that the first sensor (6) is configured to measure the ink flow derived from the first chamber (2); wherein the control system (100) is configured to control the amount of ink emitted by the ink distribution system (1) by adjusting the pressure value sent to the first chamber (2).
2. Ink distribution system, according to claim 1, characterized in that it further comprises: a second chamber (22) configured to retain ink (25) under pressure; a second ink channel (23) connecting an outlet of the second chamber to a junction (17) joining the second ink channel (23) with the first ink channel (3); a mixer (10) located at the junction (17) or downstream from the junction (17) according to the ink flow in the first ink channel (3) and configured to mix the ink derived from both chambers (2, 22) together and to emit the resulting mixture to an outlet (14) of the ink distribution system (1).
3. Ink distribution system, according to claim 2, characterized in that it further comprises: a second sensor (26) configured to measure the ink flow derived from the second chamber (22) or configured to measure the amount of ink within the second chamber (22); a second pressure source (24) configured to send air with adjustable pressure to the second chamber (22); wherein the control system (100) is configured to control the ink flow derived from the second chamber by adjusting the pressure value sent by the second pressure source (24), thereby controlling the total amount of ink sent by the ink distribution system (1) as well as the relative amount of ink derived from each chamber (2, 22).
4. Ink distribution system, according to claim 2, characterized in that it further comprises: a mixing valve (11) at the junction (17) that controls the relative amount of mixed ink derived from the first and from the second chamber (2, 22), respectively; and wherein the first pressure source (4) is connected to the first and second chamber (2, 22) to send air to both chambers (2, 22) with adjustable pressure.
5. Ink distribution system according to claim 1, characterized in that it further comprises a first ink reservoir (7) configured to send ink to the first chamber (2)
6. Ink distribution system, according to claim 2, characterized in that it further comprises: a first ink reservoir (7) configured to send ink to the first chamber (2); a second ink reservoir (27) configured to send ink to the second chamber (22).
7. Ink distribution system, characterized in that it conforms to claims 6 and 3.
8. Ink distribution system, characterized in that it conforms to claims 6 and 4.
9. Rotary printing unit, characterized in that it comprises an ink distribution system, as defined in any one of claims 3 to 4 or 7 to 8; a subsystem comprising a set of cylinders and an ink reservoir (35) configured to print a single color channel from a fixed cliché and a control mark on a medium (34); an optical sensor (37) configured to measure an optical parameter from the control mark printed on the medium (34) and connected to the control system (100); wherein an ink distribution system (1) is configured to supply the subsystem with ink; wherein the control system (100) is functionally connected to the optical sensor and is configured to vary the relative amount of ink derived from each chamber whenever the measured optical parameter deviates from a target value to match the measured optical parameter with the target value.
10. Rotary printing unit, according to claim 9, characterized in that there is no ink recirculation channel from an ink reservoir (35) to the ink distribution system configured to transport ink from the ink reservoir (35) to an ink distribution system.

Description

Field of invention [001] The present invention relates to an ink system for a printing machine. In particular, it relates to a system for delivering precise quantities of ink to the printing machine. Background of the technique [002] A printing machine is composed of several printing units; each printing unit is printing one color onto a substrate. The combination of colors results in the colored printed pattern. Modern machines offer an in-line quality control system that checks the quality of the printed material and feeds the result back to the printing units. Quality control can occur at the end of the printing process, or after each unit. In this context of quality control, the reaction time between the detection of a quality problem and its resolution is important. A printing unit can resolve a quality problem by modifying a printing parameter, such as printing pressure, ink temperature, ink composition, pattern alignment, etc. To be reactive in parameters involving ink composition or temperature, modern printing units tend to minimize the amount of ink used in the ink reservoir in direct contact with the printing apparatus. The ink reservoir can be, for example, an inkwell, a reservoir with a double scraper blade, or an ink gripper between the printing and the ink cylinder. To manage a small ink reservoir or to regulate an ink mixture, a precise ink dispensing system is necessary. Summary of the invention [003] The present invention describes an ink dispensing system that uses air pressure to control ink distribution. The dispensing system comprises a first chamber to maintain the ink under pressure. A pressure source supplies air to the chamber to adjust the pressure in the chamber. A first ink channel connects the chamber outlet to an outlet of the ink dispensing system. The pressure in the chamber is used as a parameter to control the flow (or equivalently the quantity) of ink exiting the chamber and exiting the dispensing system. A control system monitors the ink flow distributed by the system to regulate the pressure supplied to the chamber, thus adjusting the ink flow. [004] The sensor can be a flow sensor and/or a sensor that measures a level (and therefore - optionally - a volume of ink, knowing the shape and size of the container). When using a flow sensor, the sensor is placed in the ink channel. Flow is the most convenient (direct/fast reaction) value to regulate and therefore the flow sensor is the preferred solution. When using a level sensor, it can be placed inside the chamber or after the system outlet (to measure the level of ink dispensed). The volume/quantity of ink (distributed at the outlet or remaining in the chamber) is obtained using the level sensor or can be calculated by integrating the readings of a flow sensor over time. The ink flow is obtained using the flow sensor or can be calculated by deriving the readings of a level sensor over time. [005] Controlling the ink flow using pressure allows for very precise flow control. By regulating the flow, the system distributes ink continuously, even though it can interrupt and restart the flow. The use of pressure also allows for very precise control of the ink level (in the ink reservoir), since the level is the result of the accumulation of an ink flow. [006] Advantageously, to regulate the ink composition at the outlet, the system comprises a second chamber to hold ink under pressure. The ink composition in the second chamber is intended to be different from that in the first chamber. The ink exiting the second chamber is conveyed through a second ink channel. The second ink channel flows into the first ink channel at a junction point. The resulting ink mixture is processed with a mixer to obtain a homogeneous mixture. In addition, the dispensing unit comprises a second pressure source (which is part of the second ink channel) or comprises a mixing valve at the junction to control the relative amount of ink mixed from each channel. As a result, the dispensing system can control the total ink flow at the outlet of the dispensing system as well as the relative ink flow from the first and second chambers, respectively, thus controlling the ink composition. [007] In the configuration that uses the second pressure source, the second pressure source supplies air to the second chamber to adjust the chamber pressure. The system further comprises a second sensor to measure the ink flow exiting the second chamber (before the junction point with the first channel). Preferably, the first sensor is configured to measure the ink flow coming from the first chamber (in other words, it is preferably placed in the first ink channel before the mixing point). [008] In the configuration that uses the mixing valve, the first pressure source can be connected to the first and second chambers. [009] The pressure source used here is configured to set a controllable pressure value. In other words, the pressure at the output of the pressure source can be