JP3222948U - Ink jet printer having print head cleaning device - Google Patents

Abstract

An inkjet printer having a printhead cleaning device that reduces the risk of cross contamination of ink. An ink jet printer includes a print head that ejects ink onto a substrate while the substrate is being transported, and a cleaning device that is capable of relative movement with respect to the print head for cleaning the print head. The print head has a lower nozzle plate with inkjet nozzles 34. The cleaning device 50 includes an upward cleaning surface 54 with a cleaning fluid opening 56 for directing the cleaning fluid upward and toward the nozzle plate at the bottom of the print head. The printer includes a controller 46 for adjusting the ink back pressure at the ink jet nozzles configured to apply a negative printing pressure to the atmosphere and a positive purge and rinse pressure to the atmosphere. The purge pressure is higher than the rinse pressure, and the rinse pressure is higher than the printing pressure. [Selection] Figure 2

Description

  The present invention relates to an ink jet printer having a print head cleaning device.

  Inkjet printing is a well-known technique for recording an image on a substrate by controlling the ejection of the appropriate inkjet ink. In general, inkjet printer devices include multiple printheads, such as at least one printhead for each color, such as printheads for each of blue-green, magenta, yellow and black, and optionally white ink And / or additional print heads for clear ink or ink of any auxiliary color are also aligned. Each print head includes a nozzle plate with a plurality of nozzles. Ink is supplied from the ink container to the plurality of nozzles. The print head may be configured to scan the width of the substrate to be printed in a reciprocating manner. Alternatively, the print head is placed stationary in a row that covers at least the width of the substrate to be printed. The substrate may be paper or paper-based material, plastic and textile. In general, the substrate is fed by a conveyor from the supply end of the printer, through the print section where the substrate is printed, and if possible further processing such as curing or drying to the exit end. The substrate may be supplied as a separate sheet or web. The supply and discharge sections and the conveyor are generally adapted to the configuration of the substrate. For example, if the substrate to be printed is a web wound on a reel, the supply unit may include a rewind station, and the printing unit includes a support roll and / or drum that temporarily fixes the substrate. Or, in the case of textile materials, may comprise an endless conveyor belt with a tacky coating to which the substrate is temporarily bonded, and the outlet comprises a winding reel around which the printed substrate is wound. It's okay. In the case of a sheet-like substrate, a sheet feeder is applied.

  During printing, the printhead nozzles can be partially clogged by (mid) hardened / dry ink and particles / dust from the environment and / or the substrate. There is also a possibility that dust adheres to the nozzle plate. This inevitable contamination of the print head can affect the printing operation and can degrade image quality. Therefore, print head maintenance is required during operation. As part of the maintenance procedure, the printhead is frequently purged, wiped and / or rinsed to restore printing performance and image quality. Print head purging involves creating a forced flow of ink through the nozzles (at a speed much slower than the jetting speed during printing) and removing the ink without ejecting it onto the substrate. Rinsing involves contacting the nozzle plate with a dedicated cleaning solution. The print head is often wiped after purging and rinsing by contacting the nozzle plate with, for example, a rubber wiper or an ink-absorbing cloth.

  During printing, back pressure (negative pressure relative to atmospheric pressure) is applied to the ink in the nozzle, thereby creating an ink meniscus in the nozzle itself, so that the ink meniscus is retracted in the nozzle and is not released therefrom. . If the printing back pressure is maintained during maintenance, debris, cleaning liquid, and / or excess ink are sucked into the nozzle and taken into the ink contained in the nozzle. As a result, color degradation of each ink can occur, affecting the physical properties such as color strength and surface tension and viscosity, resulting in degradation of image quality. Also, cross contamination of ink from other nozzles can occur, especially when different color inks, such as those currently developed, are supplied to the nozzles of the same nozzle plate. These printheads have two or more independent ink paths for different inks.

  It is known in the art to temporarily increase the ink pressure from normal printing back pressure to a pressure higher than atmospheric pressure during maintenance. For example, Patent Document 1 discloses a liquid ejection device such as an ink jet printer having a once-through print head in which ink continuously circulates. The known device includes a wiping member that wipes the nozzle forming surface by moving relative to the nozzle forming surface while being in contact with the nozzle forming surface of the print head, and at least one of the print head and the wiping member. In contrast, the cleaning liquid supply unit that supplies the cleaning liquid, and the circulation speed of the ink that circulates between the ink storage unit and the print head can be adjusted to a second speed higher than the first speed during wiping. A circulation speed adjusting unit. It is disclosed that due to circulation at a faster speed, the back pressure of the nozzle becomes positive during the head cleaning operation, thereby preventing foreign matters remaining on the nozzle forming surface from entering the nozzle. Ink is supplied from the reservoir to the nozzles through cavities in the printhead. The reservoir itself is connected to the tank via a collection channel and a supply channel equipped with a circulation pump for generating a circulation flow. The speed and pressure of the ink circulated between the tank and the storage tank are adjusted by the ink circulation mechanism, and the ink circulation mechanism includes a pressure adjustment mechanism including another pump connected to the tank in addition to the circulation pump. In the illustrated embodiment, the cleaning liquid is supplied to a so-called ink supply surface and flows downward to a corner between the ink supply surface and the nozzle forming surface. Next, the wiper is moved in the first direction, bent in contact with the corner portion on the surface to which ink is supplied, and further moved while in contact with the nozzle formation surface. In this way, it is considered that the cleaning liquid is pushed along the nozzle formation surface from the corner portion by the wiper in order to remove dust and the like. The wiper operation is then performed in the opposite direction with or without further cleaning liquid supply. This cleaning operation can be repeated depending on the print load. Optionally, the nozzle can be purged by increasing the speed of the circulating ink to a third speed that is higher than the second speed during forward or reverse movement.

  The disadvantage of this known device is the operational complexity. Moreover, because of the forced flow of ink during the application of the cleaning fluid and the wiping of the remaining entrainment of ink, dust and other particles from the nozzle forming surface can enter the ink nozzles and even There is a possibility of entering from the ink circulation mechanism including the storage tank to the tank. Thus, ink contamination can still occur. If different color dyes are served for nozzles on the exact same printhead, there is still a risk of cross-contamination. In particular, when the ink used is a dispersible ink containing dispersible dye particles in a solvent, the nozzle is damaged by forcibly bringing the wiper into contact with the nozzle forming surface. It becomes easy. These particles can become trapped between the wiper and the nozzle forming surface, which can wear the nozzle plate and thereby adversely affect printing operations and image quality. Further, the wear of the wiper due to the particles may adversely affect the cleaning operation.

US Patent Application Publication No. 2016/0263898 Specification

  Accordingly, there is a need for an improved printhead cleaning device and its operation that reduces the risk of (cross) contamination.

  In view of that, the present invention provides an ink jet printer for printing ink on a substrate, comprising at least one ink jet print head for ejecting ink onto the substrate. A lower nozzle plate of one print head has a plurality of inkjet nozzles, a transport device for sending the substrate through the printer and under the at least one print head, and for cleaning at least one print head of the inkjet printer. A print head cleaning device, wherein the print head and the print head cleaning device are configured to move relative to each other in a maintenance position, the print head cleaning device having an upward cleaning surface, Top the cleaning fluid The controller for adjusting the back pressure of the ink in the ink jet nozzles provided in the printer is provided with at least one cleaning fluid supply element for directing towards the nozzle plate at the bottom of the print head. During a printing operation in which an image is recorded on the substrate by ejecting ink from the upper inkjet nozzle, a negative printing pressure is applied to the inkjet nozzle with respect to the atmosphere, and the inkjet nozzle is purged with ink. During the phase, a positive purge pressure is applied to the inkjet nozzle with respect to the atmosphere, and during the rinsing phase of the cleaning operation in which the nozzle plate is rinsed with the cleaning liquid supplied by the cleaning fluid supply element, the rinsing pressure is applied to the inkjet nozzle. The purge pressure is a rinsing pressure. The rinsing pressure is higher than the printing pressure.

  Inkjet printers for printing ink on a substrate include at least one printhead for applying ink to the substrate. A plurality of ink jet nozzles are provided on a nozzle plate below the ink jet print head. In one embodiment, at least one inkjet printhead is provided for each different ink, such as blue-green, magenta, yellow and black, and optional white, transparent and / or additional auxiliary colors. . In one embodiment, the ink jet printer is of a scanning type, and at least one print head is movable in the width direction of a substrate mounted on a carriage that can be driven back and forth, for example, along a support track. In another embodiment of a single pass type printer, the print head is fixed in the width direction of the printer, and multiple print heads for one type of ink cover at least the full width of the substrate to be printed. In this embodiment, the print head is fixed so that movement in the width direction is prevented, but displacement in the height direction is possible, allowing the cleaning device to pass under the print head. In yet another embodiment, the nozzle plate of an inkjet printhead has two or more independent ink paths for different inks to different ink containers. Inkjet printers include a transport device for feeding a substrate through the printer from a supply end to an exit end, the substrate being passed under a print head in a printing section. Depending on the type of ink, a curing device for curing (partially) the ink, for example a thermal dryer and / or a UV radiation source, may be provided downstream of each printhead station, A final curing device may also be provided downstream. The substrate can be any of the commonly used substrates as described above.

  The ink jet printer also includes a print head cleaning device for cleaning at least one print head of the ink jet printer. The print head and the associated cleaning device are movable relative to each other. Cleaning is performed while the print head and print head cleaning device are in the maintenance position, which is in the case of a scanning type ink jet printer, for example, just ahead of the longitudinal edge of the conveyor. As described with respect to the single pass type printer, when the printhead is fixedly mounted, a cleaning device is passed along the printhead. The cleaning device is configured to pass under the print head.

  The cleaning device has an upward cleaning surface, which faces the nozzle plate of the upper print head being cleaned with a short distance during cleaning. The cleaning surface is provided with one or more cleaning fluid supply elements such as nozzles, sprayers or simple openings that jet, spray or flow cleaning fluid. By cleaning, a well of cleaning fluid is formed on the cleaning surface and contacts the nozzle plate. The cleaning liquid immerses the nozzle plate and releases any dust, particles, and remaining ink. This liquid waste is discharged.

  The printer includes a controller for adjusting the ink back pressure at the inkjet nozzles configured to apply a negative printing pressure to the inkjet nozzles during a printing operation. The controller is also configured to apply a positive purge pressure to the atmosphere, preferably in the range of 80-500 mbar, such as 100 mbar, during the optional purge phase of the cleaning operation when the nozzles are purged with ink. ing. The controller preferably rinses within the range of -10 mbar to +10 mbar, preferably -5 mbar to +5 mbar, more preferably -3 mbar to +3 mbar during the rinsing phase of the cleaning operation in which the nozzle plate is rinsed with cleaning liquid. It is also configured to apply. The purge pressure is higher than the rinse pressure, and the rinse pressure is higher than the printing pressure.

  During the wash phase, the ink back pressure at the nozzle is adjusted by the controller to the pressure required for purging or rinsing. Advantageously, the ink flow through the print head is stopped during the rinse.

  In this way, contamination of the ink in the nozzle by dust, cleaning liquid and / or different inks is effectively avoided, and the nozzle plate is thoroughly cleaned by dipping with / without the wiper mechanism. The

In one embodiment, the controller comprises a processor and a memory that stores computer-readable instructions, and when the computer-readable instructions are executed by the processor,
Positioning the printhead and printhead cleaning device in a maintenance position;
Adjusting the back pressure at the print head nozzle to the required purge or rinse pressure;
Optionally interrupting the flow of ink through the printhead;
Purging the print head nozzles with ink;
Supplying a cleaning liquid to a cleaning fluid supply element of the print head cleaning device.

  During purging, ink flows to the discharge tray. The print head cleaning device preferably comprises at least one suction port connected to the pump means for removing the used cleaning fluid, the pump means comprising at least one suction port for removing liquid waste Is configured to apply a reduced pressure. After the nozzle plate is exposed to the cleaning liquid, a reduced pressure is generated, eg, by suction using a vacuum pump, to further remove any liquid waste adhering to the nozzle plate. Thus, the instructions include actuating the pump means such that a reduced pressure is generated at the at least one inlet to remove liquid waste from the nozzle plate. In general, since the cleaning device and the print head move relative to each other in the length direction of the print head, a suction port, preferably a slit that covers the width of the print head, is advantageously seen in the direction of relative movement. Positioned downstream of the cleaning liquid opening. The washing cycle is then advantageously carried out only during one-way relative movement, and during the return movement to the starting position, suction is continued but no washing cycle is carried out.

  The wiping element provided in the print head cleaning device, if any, is preferably arranged downstream of the cleaning fluid supply element and upstream of the suction port.

  The invention is further illustrated by the accompanying figures.

1 is a diagram illustrating an embodiment of an inkjet printer having a print head cleaning device according to the present invention. 1 is a schematic diagram of one embodiment of a print head cleaning device associated with a print head being cleaned. FIG. It is a figure which shows an example of the system which defines the computer readable instruction for controllers. It is a figure which shows an example of the back pressure in the nozzle during printing and a maintenance.

  In FIG. 1, the entire inkjet printer is indicated by reference numeral 10. In the illustrated embodiment, the supply unit 12 included in the printer 10 includes a rewind roll that supplies the substrate 14 to be printed. The printer also comprises a printing unit 16 comprising a number of printing stations 18, each printing station 18 comprising at least one inkjet print head 20 movable in the width direction of the printer. There may be a curing device (not shown) between adjacent printing stations, and a final curing device 22 such as a UV radiation source or a thermal dryer may also be located downstream of the printing section 16. At the outlet 24, the substrate 14 printed at this time is collected and wound, for example, on a reel 26 as shown. Transport of the substrate 14 through the printer is accomplished by rollers 28, some of which are connected to a suitable (electrical) drive (not shown) under the control of a controller 30. The print head maintenance position is adjacent to one of the longitudinal edges of the conveyor.

  FIG. 2 shows a schematic diagram of one embodiment of a printhead cleaning device 50 associated with an array of printheads 20 being cleaned (separated schematically by dashed lines). Each print head 20 includes a lower nozzle plate 32 provided with a plurality of nozzles 34. The nozzles 34 of each printhead 20 are in fluid communication with a common ink container 36 via an internal ink flow channel 38 and a supply conduit 40 and a return conduit 42. An ink flow is generated in the supply conduit 40 by the pump 44 and the flow and pressure controller 46. The back pressure is controlled by a flow and pressure controller 46 comprising a processor 48 and memory 49.

  The cleaning device 50 includes a cleaning body 52 having an upper cleaning surface 54. The surface 54 is provided with a plurality of cleaning fluid supply elements 56 which are openings in this embodiment, and are connected to the pump 59 and the cleaning liquid reservoir 60 by an internal manifold 58. The cleaning device 50 can move in the width direction of the printer relative to the print head 22 as indicated by arrow A. Along one edge of the cleaning surface 54, one or more drain channels 62 are provided to discharge liquid waste overflowing the cleaning surface to a waste container (not shown). As seen in the indicated width direction, the rear portion (downstream end) 64 of the cleaning body 52 is provided with a suction port 66 connected to a suitable suction device 68 such as a vacuum pump. During cleaning, the cleaning liquid supplied through the cleaning opening 56 forms a well 70 at the top of the cleaning surface, and the well 70 contacts the nozzle surface 32 of the print head 22 and flows to the side edge where it is drain channel 62. Discharged through. The droplets adhering to the nozzle plate 32 are removed by the wiper 72 and sucked through the suction port 66 under the operation of the suction device 68.

  FIG. 3 shows a method 80 of commands instructed as steps S1 to S9 relating to the execution of the cleaning operation after printing is stopped.

  In S1, the print head and the cleaning device are positioned relative to each other in the cleaning position. Optionally, in S2, the back pressure is adjusted from a negative (printing) pressure to a positive purge pressure. Next, nozzle purge using ink is executed in S3. After the optional purge, the back pressure is set to a rinse pressure that is lower than the purge pressure and higher than the printing pressure, and optionally the ink flow is interrupted in S4. In the next step S5, the suction port is evacuated. Subsequently, in S6, the nozzle plate is rinsed with a cleaning solution. After rinsing, suction is stopped in S7. In S8, the back pressure at the nozzle is adjusted to a negative printing pressure and ink flow is resumed if applicable. In S9, the print head is returned to the printing position and the cleaning device is returned to the inactive rest position. At that time, the printer is in a state of performing subsequent printing processing.

FIG. 4 illustrates back pressure relative to atmospheric pressure as a function of a continuous process performed in the printer according to the scheme of FIG. As is evident, the purge pressure is positive, but the rinse pressure is in a working area delimited by P _{RINSE max} and P _{RINSE min} , such as ± 3 mbar around atmospheric pressure.

10 Inkjet printer
12 Supply section
14 Substrate
16 Printing section
18 printing station
20 Print head
22 Curing device
24 Exit
26 reel
28 rollers
30 controller
32 Nozzle plate
34 nozzles
36 Ink container
38 Ink flow channel
40 Supply conduit
42 Return conduit
44 Pump
46 Flow and pressure controller
48 processor
49 memory
50 Printhead cleaning device
52 Cleaning body
54 faces
56 Cleaning fluid supply element
58 Internal manifold
59 Pump
60 Cleaning fluid storage tank
62 drain channel
64 Rear part (downstream end) of cleaning object
66 Suction port
68 Aspirator
70 wells
72 Wiper

Claims (11)

An inkjet printer (10) for printing ink on a substrate,
At least one printhead (20) for ejecting ink onto the substrate, comprising a lower nozzle plate (22) with a plurality of inkjet nozzles (34); and ,
A conveying device (28) for sending the substrate through the printer and under the at least one print head;
A print head cleaning device (50) for cleaning the at least one print head of the inkjet printer;
The print head (20) and the print head cleaning device (50) are configured to move relative to each other in a maintenance position;
The print head cleaning device (50) includes an upward cleaning surface (54), and the upward cleaning surface (54) has cleaning fluid upward and toward the lower nozzle plate of the print head. At least one cleaning fluid supply element (56) for directing,
The printer (10) includes a controller (47) for adjusting the back pressure of the ink in the inkjet nozzle, and the controller (47) removes ink from the inkjet nozzle (34) on the substrate. During a printing operation in which an image is recorded on the substrate by jetting, a negative printing pressure with respect to the atmosphere is applied to the inkjet nozzle, and the inkjet nozzle (34) is purged with ink. During the rinsing phase of the cleaning operation, a positive purge pressure with respect to the atmosphere is applied to the inkjet nozzle and the nozzle plate (22) is rinsed with a cleaning liquid supplied by the cleaning fluid supply element. The rinsing pressure is applied to the inkjet nozzle, and the purge pressure is higher than the rinsing pressure. The rinse pressure is higher than the printing pressure, ink jet printers.   2. The inkjet printer according to claim 1, wherein the purge pressure is in a range of 80 to 500 mbar with respect to atmospheric pressure.   The inkjet printer according to claim 1 or 2, wherein the rinsing pressure is in the range of -10mbar to + 10mbar, preferably -5mbar to + 5mbar, more preferably -3mbar to + 3mbar with respect to atmospheric pressure.   The inkjet printer according to any one of claims 1 to 3, wherein the controller (47) is configured to interrupt the flow of ink through the inkjet printhead (20) during a cleaning operation. . The controller (47) comprises a processor (48) and a memory (49) storing computer readable instructions (S1-S9), and when the computer readable instructions are executed by the processor,
Positioning the print head (20) and the print head cleaning device (50) in a maintenance position;
Adjusting the back pressure in the inkjet nozzle (34) to the required purge pressure or the rinse pressure;
Optionally interrupting the flow of ink through the printhead (20);
Purging the print head nozzle (34) with ink;
5. An inkjet printer according to claim 1, wherein the inkjet printer performs a process comprising: supplying a cleaning liquid to a cleaning fluid opening (56) of the print head cleaning device (50).   The print head cleaning device (50) comprises at least one suction port (66), the at least one suction port (66) is a pressure reduced to the at least one suction port to remove liquid waste 6. Inkjet printer according to any one of the preceding claims, connected to pump means (68) configured to apply   Said command activating said pump means (68) such that a reduced pressure is generated at said at least one inlet (66) to remove liquid waste from said nozzle plate (22); The inkjet printer according to claim 5, further comprising:   The print head (20) is fixed in the width direction of the printer (10), and the cleaning device (50) is moved in the width direction of the printer (10) during the cleaning operation. The inkjet printer according to claim 1, wherein the inkjet printer is configured.   The print head (20) is configured to move in the width direction of the printer (10), the maintenance position is along the longitudinal side of the printer (10), and the cleaning device (50) The ink jet printer according to any one of claims 1 to 7, wherein the ink jet printer is configured to move relative to the print head (20) during the cleaning operation.   10. Inkjet printer according to any one of the preceding claims, wherein the cleaning device (50) is configured to perform a cleaning operation during movement in one direction.   The inkjet printhead (20) comprises a nozzle plate (22) having inkjet nozzles (34), and two or more for different inks from different ink containers to different nozzles (34) in the printhead (20) The inkjet printer according to claim 1, wherein an independent ink path is provided.