Indirect printing system

Patent metadata

Field	Value
Publication number	US-11660857-B2
Application number	US-202117551219-A
Country	US
Kind code	B2
Filing date	Dec 15, 2021
Priority date	Mar 20, 2015
Publication date	May 30, 2023
Grant date	May 30, 2023

Abstract

An indirect printing system is disclosed having an intermediate transfer member (ITM) in the form of an endless belt that circulates during operation to transport ink images from an image forming station. Ink images are deposited on an outer surface of the ITM by one or a plurality of print bars. At an impression station, the ink images are transferred from the outer surface of the ITM onto a printing substrate. In some embodiments, the outer surface of the ITM 20 is maintained within the image forming station at a predetermined distance from the one or each of the print bars 10, 12, 14 and 16 by means of a plurality of support rollers 11, 13, 15, 17 that have a common flat tangential plane and contact the inner surface of the ITM. In some embodiments, the inner surface of the ITM is attracted to the support rollers, the attraction being such that the area of contact between the ITM and each support roller is greater on the downstream side than the upstream side of the support roller, referenced to the direction of movement of the ITM.

First claim

The invention claimed is:

1. An indirect printing system having an intermediate transfer member (ITM) in the form of a circulating endless belt for transporting ink images from an image forming station, where the ink images are deposited on an outer surface of the ITM by at a plurality of print bars, to an impression station where the ink images are transferred from the outer surface of the ITM onto a printing substrate, wherein the outer surface of the ITM is maintained within the image forming station at a predetermined vertical distance from the print bars by a plurality of support rollers that have a common flat tangential plane and contact the inner surface of the ITM, the support rollers being disposed such that a different respective support roller is both (i) located below and (ii) vertically aligned with each print bar of the plurality of print bars, wherein each given support roller of the plurality of support rollers is associated with a respective rotational-velocity measurement device and/or a respective encoder for measuring a respective rotational-velocity of the given support roller wherein at least one condition selected from the group consisting of a first condition, a second condition, and a third condition is true, and wherein:
I. according to the first condition, for each given print bar of the plurality of print bars, a respective vertically-aligned support roller is disposed slightly downstream of the given print bar;
II. according to the second condition, the system further comprises:
droplet-deposition control circuitry configured to regulate, for each given print bar of the plurality of print bars, a respective rate of ink droplet deposition DR onto the ITM, the droplet-deposition control circuitry regulating the ink droplet deposition rates in accordance with and in response to the measured of the rotational velocity of a respective support rollers that is vertically aligned with the given print bar; and
III. according to the third condition, for upstream and downstream print bars respectively vertically aligned with upstream and downstream support rollers, the droplet-deposition control circuit regulates respective deposit rates DR UPSTREAM , DR DOWNSTREAM deposition rates at upstream and downstream print bars so that a difference DR UPSTREAM −DR DOWNSTREAM between respective ink-droplet-deposition-rates at upstream and downstream print bars is regulated according to a difference function between function F=ω UPSTREAM *R UPSTREAM −ω DOWNSTREAM *R DOWNSTREAM where: i. ω UPSTREAM is the measured rotation rate of the upstream-printbar-aligned support roller that is measured by its associated rotational-velocity measurement device or encoder; ii. R UPSTREAM is a radius of an upstream roller of the plurality of support rollers; iii. ω DOWNSTREAM is the measured rotation rate of the downstream-printbar-aligned support roller that is measured by its associated rotational-velocity measurement device or encoder; and ii. R DOWNSTREAM is a radius a downstream roller of the plurality of support rollers.

2. The indirect printing system as claimed in claim 1 wherein at least the first condition is true.

3. The indirect printing system as claimed in claim 1 wherein at least the second condition is true.

4. The indirect printing system as claimed in claim 1 wherein at least the third condition is true.

5. The indirect printing system as claimed in claim 1 , wherein each measurement device and/or the encoder is attached to its respective roller.

6. The indirect printing system as claimed in claim 1 , wherein each measurement device and/or the encoder directly monitors rotation of its respective associated roller or of a rigid object that is rigidly attached to the roller the respective associated roller and rotates in tandem therewith.

7. The indirect printing system as claimed in claim 1 , wherein each measurement device and/or the encoder includes at least one motion-tracking sensor selected from the sensor group consisting of: (i) a magnetic sensor; (ii) an optical sensor and (iii) a mechanical sensor, the at least one motion-tracking sensor configured to track angular motion of its respective roller.

8. The indirect printing system as claimed in claim 1 wherein the inner surface of the ITM is attracted to the support rollers, the attraction being such that the area of contact between the ITM and each support roller is greater on the downstream side than the upstream side of the support roller, referenced to the direction of movement of the ITM.

9. The indirect printing system as claimed in claim 8 wherein the inner surface of the ITM and the outer surface of each support roller are formed of materials that tackily adhere to one another, adhesion between the outer surface of each support roller and the inner surface of the ITM serving to prevent the ITM from separating from the support rollers, during operation, when the belt circulates.

10. The indirect printing system as claimed in claim 9 wherein an inner surface of the ITM is coated with a material that tackily adheres to the surfaces of the support rollers.

11. A method of operating an indirect printing system having an intermediate transfer member (ITM) in the form of a circulating endless belt, the method comprising:
at an image forming station of the indirect printing system, depositing ink images on an outer surface of the ITM by at a plurality of print bars;
transporting the images from the image forming station to an impression station of the indirect printing system; and
at the impression station, transferring the ink images from the outer surface of the ITM onto a printing substrate,
wherein the outer surface of the ITM is maintained within the image forming station at a predetermined vertical distance from the print bars by a plurality of support rollers, the support rollers (i) having a common flat tangential plane; (ii) contacting the inner surface of the ITM; and (iii) being disposed such that a different respective support roller is located below and vertically aligned with each print bar of the plurality of print bars, and wherein the method further comprises:
for each given support roller of the plurality of support rollers, monitoring a respective rotational velocity of the given support roller by operating at least one monitoring-device selected from the group consisting of: (i) a respective rotational-velocity measurement device that is respectively associated with said each given support roller; and (ii) a respective encoder to measure the respective rotational-velocity of said each given support roller,
wherein the method is performed such that at least one condition selected from the group consisting of a first condition, a second condition, and a third condition is true, and wherein:
I. according to the first condition, the method further comprises:
for each given print bar of the plurality of print bars, a respective vertically-aligned support roller is disposed slightly downstream of the given print bar;

II. according to the second condition, the method further comprises:
in accordance with and in response to the measured of the rotational velocity of a respective support rollers that is vertically aligned with the given print bar, respectively regulating, for each given print bar of the plurality of print bars, a respective rate of ink droplet deposition DR onto the ITM; and

III. according to the third condition, the method further comprises:
for upstream and downstream print bars respectively vertically aligned with upstream and downstream support rollers, regulating respective deposit rates DR UPSTREAM , DR DOWNSTREAM deposition rates at upstream and downstream print bars so that a differe

Assignees

• Landa Corp Ltd

Inventors

• Landa Benzion
• Shmaiser Aharon
• Siman-Tov Alon
• Levy Alon

Classifications

• B41J11/04 Primary

  Roller platens · CPC title

• B41J2/0057 Primary

  where an intermediate transfer member receives the ink before transferring it on the printing material · CPC title

• B41N10/04

  multi-layer · CPC title

• B41J2/01 Primary

  Ink jet · CPC title

• B41J2002/012

  with intermediate transfer member · CPC title