System and method for reducing ink contamination on a printhead faceplate during inkjet printhead maintenance - Patents.com

Abstract

To provide a mechanism useful for securing high-quality wiping over the entire surface of an inkjet array in a printhead faceplate.SOLUTION: An inkjet printhead assembly includes a controller operatively connected to an actuator so the controller can operate the actuator to tilt a carrier plate in which a plurality of printheads are mounted after a purge of the printheads has been performed. The tilt assists gravity in directing the purged ink to a wiper that is moved by another actuator operated by the controller to wipe the faceplates of one or more printhead faceplates in the carrier plate. After the wiper is returned to its home position, the carrier plate is returned to its level position and the printhead assembly is returned to its operational position for printing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This disclosure relates generally to inkjet printing systems, and more particularly to maintenance of printheads in such printers. [Background technology]

[0002] Large scale inkjet printers have long print runs with little downtime and can be used over multiple shifts at a printing facility. During print production, the printheads of these printers require periodic ink purging through the inkjets and wiping of the printhead faceplate while ink is still present on the faceplate to maintain proper jetting functionality and good image quality. The coating of the inkjet printheads of these printers is hydrophobic to prevent ink from leaking out of the inkjet nozzles onto the faceplate. This hydrophobic coating causes ink to retreat from the edges of the inkjet array in the faceplate, forming large droplets. In addition, the inkjet nozzles are held at a small negative pressure after ink is removed during purging. This negative pressure also results in ink retreating further away from the edges of the inkjet array and back into the nozzles. Once the purge is complete, the faceplate is wiped with an elastomeric wiper to remove the purged ink from the faceplate. This wiping occurs after a time delay from the end of the purge sequence due to system constraints within the printer. As a result, at the beginning of a wipe, there may not be enough ink at the end of the inkjet array where the wipe begins to lubricate the wiper for a smooth wipe of the faceplate. Instead, at the beginning of the wipe, ink may smear against the faceplate, and this smeared ink may partially close or otherwise damage nozzles in the array located at the beginning of the wipe. These damaged or non-functional inkjets may result in poor image quality. It would be beneficial to ensure a good quality wipe across the entire inkjet array. Summary of the Invention [Problem to be solved by the invention]

[0003] The new printhead assembly includes a mechanism that helps ensure a good quality wipe across the surface of the inkjet array in the printhead faceplate. The printhead assembly includes a carrier plate having a length and a width, a plurality of printheads attached to the carrier plate, a member configured to perform linear motion positioned at one end of the length of the carrier plate, a plurality of actuators, at least one actuator operably connected to the member configured to perform linear motion, and a controller operably connected to the plurality of actuators. The controller is configured to operate the at least one actuator to move the member configured to perform linear motion to move one end of the carrier plate and tilt the carrier plate, and to operate the at least one actuator to reverse the movement of the member configured to perform linear motion to return the carrier plate to a level position.

[0004] New inkjet printers include printhead maintenance systems that help ensure a good quality wipe across the surface of the inkjet array in the printhead faceplate. The inkjet printer includes a printhead assembly having a carrier plate having a length and a width, a plurality of printheads attached to the carrier plate, a member configured to perform linear motion positioned at one end of the length of the carrier plate, a plurality of actuators, a first actuator operably connected to the member configured to perform linear motion, and a controller operably connected to the plurality of actuators, the controller being configured to operate the first actuator to move the member configured to perform linear motion to move one end of the carrier plate and tilt the carrier plate, and to operate the first actuator to reverse the linear motion of the member configured to perform linear motion to return the carrier plate to a level position; and a wiper operably connected to a second actuator in the plurality of actuators, the controller being further configured to operate the second actuator in the plurality of actuators to move the wiper from a first position across a faceplate of at least one printhead attached to the carrier plate and to return the wiper to the first position after the wiper has traversed the faceplate of the at least one printhead.

[0005] A method of operating a printhead maintenance system in an inkjet printing system helps ensure a quality wipe across a surface of an inkjet array in a printhead faceplate, the method including: operating, with a controller, a first actuator in a plurality of actuators to move a member configured to perform linear motion to tilt a carrier plate on which a plurality of printheads are mounted, operating, with the controller, a second actuator in the plurality of actuators to move a wiper from a first position across a faceplate of at least one printhead mounted on the carrier plate and returning the wiper to the first position after the wiper has traversed the faceplate of the at least one printhead, and operating, with the controller, the at least one actuator to reverse the linear motion of the member configured to perform linear motion to return the carrier plate to a level position. [Brief description of the drawings]

[0006] The foregoing aspects and other features of an inkjet printing system that helps ensure a quality wipe across the surface of an inkjet array in a printhead faceplate, and its method of operation, are set forth in the following description taken in conjunction with the accompanying drawings.

[0007] [Figure 1] FIG. 1 is a side view of a printhead assembly in an inkjet printing system that helps ensure a good quality wipe across the surface of an inkjet array in a printhead faceplate.

[0008] [Diagram 2] FIG. 2 is a bottom view of the wiper and carrier plate shown in FIG.

[0009] [Diagram 3] FIG. 3 illustrates the effect of a carrier plate on ink purged from ink jets in a printhead of the printhead assembly of FIG.

[0010] [Figure 4] FIG. 4 is a flow diagram of a process for operating the printhead assembly of FIG. 1 and the wiper of FIG. 2 to ensure a good quality wipe across the surface of the inkjet array in the printhead faceplate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] For a general understanding of the present embodiments, reference is made to the drawings, in which like reference numbers are used throughout to designate like elements.

[0012] FIG. 1 is a side view of a printhead assembly 100 in an inkjet printing system that helps ensure a good quality wipe across the surface of the inkjet array in the printhead faceplate. The system 100 includes a support 104 to which a printhead array carrier plate 108 is attached. In the embodiment shown in FIG. 1, three printheads 112A, 112B, and 112C are mounted in an orientation that allows the inkjets in the printheads to eject ink drops into a printhead cap 116. As used herein, the term "carrier plate" refers to any structure that holds multiple printheads in precise alignment with one another. The cap 116 mates with the carrier plate 108 to seal the environment of the inkjet array of printheads 112A, 112B, and 112C when purge cycles and wipes of the faceplate occur. A wiper 120 is positioned in a home position shown in FIG. 1 to wipe the printhead faceplate in the direction W shown in the figure. As described in more detail below, the carrier plate 108 is positioned at an angle after purging the printheads as shown in FIG. 1 and before the wiper 120 is moved to perform a wipe of the faceplate. The three printheads 112A, 112B, and 112C are positioned such that the longitudinal axes of the inkjet arrays of printheads 112A and 112B are aligned but spaced apart a distance corresponding to the length of printhead 112C. Printhead 112C is offset from the aligned longitudinal axes of printheads 112A and 112C such that the three printheads form a single array of inkjets having the width of the largest media sheet that can be printed by the printhead assembly.

[0013] FIG. 2 shows the wiper 120 in more detail in its home position. The wiper 120 is fixedly mounted to a wiper carrier 204, which is slidably mounted to a wiper slide 208 for reciprocating motion along the wiper slide to wipe the faceplate 212C of the printhead 112C and the faceplate of the printhead 112A (not shown in FIG. 2). To effectuate the movement of the wiper carrier and the tilting of the carrier plate 108, a controller 220 is operably connected to a number of actuators 224, which are operably connected to the wiper carrier 204 and the lead screw 216. The controller 220 operates at least one of the actuators 224 to rotate the lead screw 216, advancing the screw and pushing the end of the carrier plate closest to the wiper 120 toward the printhead cap 116. As used herein, the term "lead screw" means any component that converts rotary motion into linear motion. Although the member that tilts the carrier plate back to a level position is shown as being a rotating member, it may be a linear member that moves in a reciprocating linear fashion. Following printhead purging, this tilting of the carrier plate 108 allows ink on the printhead faceplate to flow toward the end of the carrier plate that is closest to the wiper 120 home position. This flow is facilitated by the hydrophobic coating of the inkjet arrays of the printheads 112A, 112B, and 112C. This hydrophobic coating of the printhead faceplate in the area where the inkjet arrays are located helps to retain ink that collects on the printhead faceplate during printing operations between the nozzles in the faceplate and away from the end of the inkjet array that is aligned with the longitudinal axis of the faceplate. Tilting the carrier plate 108 moves the ink toward the wiper 120 home position where the ink contacts or is very close to the wiper 120.Thus, as the controller 220 operates another actuator 224 to slide the wiper carrier 204 along the wiper slide 208, the relatively fresh ink lubricates the wiper 120 and helps to clean rather than smudge the printhead faceplate (FIG. 3). After wiping is completed, the controller 220 operates the actuator 224 to return the wiper to its home position. The controller 220 then operates one of the actuators to rotate the lead screw 216 in the opposite direction to that which it was previously rotated to return the carrier plate to its level position. The cap 116 can then be removed from the printhead assembly 100 so that the assembly can be returned to its operational printing position. Only the wiper 120 for cleaning the faceplates of the printheads 112C and 112A is shown in the figures, but another wiper for cleaning the printhead 112B is mounted to a wiper carrier that is slidably mounted to a wiper slide that is parallel to the wiper carrier 204 and the wiper slide 208. Another actuator 224 operates simultaneously to move the wiper 120 by actuating the actuator 224 to move the wiper carrier to clean the faceplate of the printhead 112B. In one embodiment, the tilt of the carrier plate ranges from about 1 inch to about 2 inches below the horizontal axis of the carrier plate when the carrier plate is horizontal.

[0014] A process 400 for operating the printhead assembly 100 and wiper 120 in a manner that helps ensure a quality wipe across the surface of the inkjet array in the printhead faceplate is shown in FIG. 4. In the description of the process, a statement that the process performs a certain task or function refers to a controller or general-purpose processor executing program instructions stored in a non-transitory computer-readable storage medium operably connected to the controller or processor to operate on data or to operate one or more components in the printer to perform the task or function. The controller 220 described above can be such a controller or processor. Alternatively, a controller can be implemented with two or more processors and associated circuits and components, each configured to form one or more tasks or functions described herein. Additionally, the elements of the method can be performed in any feasible chronological order, regardless of the order shown in the figures or the order in which the processes are described.

[0015] The process 400 begins by moving the printhead assembly to its maintenance station and capping the printhead (block 404). A pressure source is then operated by the controller 220 at a predetermined pressure for a predetermined time to purge the inkjets in the printhead (block 408). Another actuator is operated to rotate a lead screw and tilt the carrier plate toward the wiper(s) (block 412). After tilting of the carrier plate is completed and a predetermined time interval has expired (block 416), the actuator(s) are operated to move the wiper(s) along the wiper slide(s) to clean the printhead faceplate (block 420). Once wiping is completed (block 424), the actuator(s) moving the wiper(s) along the wiper slide(s) are reversed to return the wiper(s) to the home position(s) (block 428). The wipe is determined to be complete when the wiper passes over the last inkjet array in the last printhead wiped by the wiper. The actuator that rotates the leadscrew is operated to reverse rotation of the leadscrew and return the carrier plate to its level position (block 432). The printhead assembly is then uncapped and returned to its operating position for printing (block 436).

[0016] The predetermined time interval should be sufficient to allow a portion of the purged ink on the faceplate of the printhead closest to the wiper to flow toward the wiper and contact the wiper for lubrication at the start of the wiping action. In one embodiment, the predetermined time interval is about 25 to about 35 seconds, with 30 seconds being a typical time interval for a faceplate coated with a hydrophobic coating. Other time intervals can be used depending on the amount of ink purged from the inkjets and the presence or absence of a coating on the faceplate of the printhead closest to the wiper.

[0017] It will be appreciated that variations of the above-disclosed devices and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen substitutions, modifications, variations, or improvements may subsequently be made by those skilled in the art that are also intended to be encompassed by the following claims.

Claims

1. 1. An inkjet printer, comprising: a print head assembly having a carrier plate having a length and a width, a plurality of print heads attached to the carrier plate, a member configured to perform linear motion positioned at one end of the length of the carrier plate, a plurality of actuators, a first actuator operably connected to the member configured to perform linear motion, and a controller operably connected to the plurality of actuators, the controller being configured to operate the first actuator to move the member configured to perform linear motion to move the one end of the carrier plate from a level position to tilt the carrier plate so that the one end of the length of the carrier plate has a different gravitational potential than the other end of the length of the carrier plate, and to operate the first actuator to reverse the linear motion of the member configured to perform linear motion to return the carrier plate to the level position; a wiper operably connected to a second actuator in the plurality of actuators, wherein the controller is further configured to operate the second actuator in the plurality of actuators to move the wiper from a first position across a faceplate of at least one printhead mounted on the carrier plate between the one end and the other end of the length while the carrier plate is tilted, and to return the wiper to the first position while the carrier plate is tilted after the wiper has traversed the faceplate of the at least one printhead between the one end and the other end of the length.

2. The member configured to undergo linear motion is also configured to rotate about a longitudinal axis of the member, and the controller further comprises:

2. The printer of claim 1, further configured to operate the first actuator to rotate the member configured for linear and rotational motion to tilt the carrier plate, and to operate the first actuator to reverse rotation of the member configured for linear and rotational motion to return the carrier plate to the level position.

3. The printer of claim 2 , wherein the member configured for linear motion and rotation about a longitudinal axis of the member is a lead screw.

4. 4. The printer of claim 3, wherein the inclination of the carrier plate is within a range of 1 inch to 2 inches below a horizontal axis when the carrier plate is in the level position.

5. 5. The printer of claim 4, wherein each of the printheads in the plurality of printheads has a faceplate having an area in which an array of inkjets is located, and a hydrophobic coating covers the area of ​​each faceplate in which the array of inkjets is located.

6. The controller:

5. The printer of claim 4, further configured to operate a pressure source operably connected to the printhead in the printhead assembly to eject ink from the inkjets in an array of inkjets onto the faceplate of the printhead prior to operating the first actuator to tilt the carrier plate.

7. The controller:

7. The printer of claim 6, further configured to wait a predetermined time interval after operating the first actuator to tilt the carrier plate so that the ejected ink flows toward the first position of the wiper.

8. 8. The printer of claim 7, wherein the predetermined time interval is sufficient for a portion of the ejected ink to contact the wiper at the first location.

9. 9. The printer of claim 8, wherein the predetermined time interval is in the range of 25 to 35 seconds.

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