Method and system for priming a dry printhead - Patents.com

Abstract

A system for priming a dry inkjet printhead (4) includes an inkjet printhead (4) having an inlet port (8) connected to an upstream ink line and an outlet port (14) connected to a downstream ink line, a pump (40) operably connected to the downstream ink line, a capper (200) engaged with the printhead, a vacuum source for applying suction to a capping chamber (202) of the capper (200), and a control system for coordinating activation of the pump and vacuum source. In use, the pump (40) is activated simultaneously with the vacuum source, thereby drawing ink through the printhead (4) from the inlet port to the outlet port, priming the printhead.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to a method and system for priming a dry printhead. The present invention has been developed primarily to facilitate the transport of dry or unprimed page-wide printheads that do not contain any transport fluid. [Background technology]

[0002] 2. Background of the Invention Inkjet printers employing Memjet® technology are commercially available for many different print formats, including small office home office ("SOHO") printers, label printers, and wide format printers. Memjet® printers typically have one or more stationary, user-replaceable inkjet printheads. For example, SOHO printers have a single user-replaceable multi-color printhead, high-speed inkjet presses have multiple user-replaceable single-color printheads aligned along the media feed direction, and wide format printers have multiple user-replaceable printheads that are staggered and overlapping to span a large page width.

[0003] A replacement printhead may be shipped in a "wet" or "dry" state for installation in an inkjet printer by a user. Typically, printheads are shipped in a "wet" state to avoid potential issues with priming during installation. A wet transport printhead may be filled with ink or transport fluid, which is typically an ink vehicle lacking colorant.

[0004] However, wet transport printheads are less convenient for users because ink or transport fluid may leak from the printhead during shipping and / or spill during the installation process. Users would prefer to receive dry printheads, which are not prone to leaking or spilling during shipping or installation. Summary of the Invention [Problem to be solved by the invention]

[0005] However, dry transport printheads present challenges for the ink delivery systems used to prime the dry printheads with ink. Therefore, it is desirable to provide a method and system for priming a dry printhead, such as a replacement printhead being newly installed in an inkjet printing system. [Means for solving the problem]

[0006] Summary of the Invention As used herein, the term "ink" is intended to mean any printing fluid that can be printed from an inkjet printhead. Ink may or may not contain a colorant. Thus, the term "ink" can include traditional dye-based or pigment-based inks, infrared inks, fixatives (e.g., precoats and finishes), 3D printing fluids, and the like.

[0007] As used herein, the term "printer" refers to any printing device for making marks on a print medium, such as a traditional desktop printer, a label printer, a reproduction device, a copier, a digital inkjet press, or the like.

[0008] BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0009] [Figure 1] 1 illustrates a schematic of an ink delivery system for a printer having a replaceable inkjet printhead. [Diagram 2] 1 illustrates a schematic of a system for priming a dry inkjet printhead. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Detailed Description of the Invention Gravity Feed Ink Delivery System 1, there is shown a schematic of a printer having an ink delivery system 1 for supplying ink to a printhead 4. The ink delivery system is a gravity-fed system similar in function to the systems described in U.S. Patent Application Publication Nos. 2011 / 0279566 and 2011 / 0279562, the contents of which are incorporated herein by reference.

[0011] The ink delivery system comprises an intermediate ink tank 100 having an ink outlet port 106 connected to a printhead inlet port 8 of the printhead 4 via a first ink line 10. An ink return port 108 of the intermediate ink tank 100 is connected to a printhead outlet port 14 of the printhead 4 via a second ink line 16. Thus, the intermediate ink tank 100, the first ink line 10, the printhead 4 and the second ink line 16 define a closed fluid loop. Typically, the first ink line 10 and the second ink line 16 consist of flexible tubing of a certain length.

[0012] The printhead 4 is user replaceable by a first connection 3 that removably interconnects a printhead inlet port 8 with a first ink line 10 and a second connection 5 that removably interconnects a printhead outlet port 14 with a second ink line 16. The printhead 4 is typically a page-wide printhead, and may be, for example, a printhead as described in U.S. Patent Application Publication No. 2011 / 0279566, U.S. Patent No. 10,384,461, or U.S. Patent No. 10,293,609, the contents of each of which are incorporated herein by reference. Such a printhead has one or more ink channels that interconnect the inlet port 8 with the outlet port 14.

[0013] The intermediate ink tank 100 is vented to atmosphere through a gas port in the form of an air vent 109 located in the roof of the tank. Thus, during normal printing, ink is supplied to the printhead 4 under gravity at a negative static pressure ("back pressure"). In other words, gravity feed of ink from the intermediate ink tank 100 located below the printhead 4 provides a pressure regulation system for supplying ink to the printhead at a predetermined negative static pressure. The amount of back pressure experienced by the nozzle plate 19 of the printhead 4 depends on the height h of the nozzle plate above the level 20 of ink in the intermediate ink tank 100.

[0014] Ink is supplied to the ink inlet port 110 of the intermediate ink tank 100 from a bulk ink reservoir comprising a collapsible ink bag 23 housed in a cartridge 24. The cartridge 24 is vented to atmosphere via a cartridge vent 25, allowing the collapsible ink bag 23 to collapse as ink is consumed by the system. The collapsible ink bag 23 is typically an air impermeable foil bag containing degassed ink which is supplied to the ink inlet port 110 via an ink supply line 28. The cartridge 24 is typically user replaceable and connected to the ink supply line 28 via a suitable ink supply connection 32.

[0015] The control system is used to maintain a substantially constant level of ink in the intermediate ink tank 100, and therefore a constant height h and corresponding back pressure. As shown in FIG. 1, a control valve 30 is positioned in the ink supply line 28 to control the flow of ink from the cartridge 24 to the intermediate ink tank 100. The control valve 30 operates under the control of a first controller 107 that receives feedback from a "high" sensor 102 and a "low" sensor 104 (e.g., optical sensors) positioned on the sidewall of the intermediate ink tank 100. When the level 20 of ink falls below the "low" sensor 104, the first controller 107 sends a signal to open the valve 30, and when the level of ink reaches the "high" sensor 102, the controller sends a signal to close the valve. In this way, the level 20 of ink in the intermediate ink tank 100 can be maintained relatively constant. The intermediate ink tank 100 may be, for example, as described in U.S. Pat. No. 10,427,414, the contents of which are incorporated herein by reference.

[0016] The closed fluid loop incorporating the intermediate ink tank 100, the first ink line 10, the printhead 4, and the second ink line 16 facilitates priming, depriming, and other necessary fluid operations. The second ink line 16 includes a peristaltic pump 40 that circulates ink through the fluid loop in a clockwise direction as shown in FIG.

[0017] The pump 40 cooperates with a pinch valve arrangement 42 to regulate the various fluid actuations. The pinch valve arrangement 42 includes a first pinch valve 46 and a second pinch valve 48 and may take the form of, for example, any of the pinch valve arrangements described in U.S. Patent Application Publication No. 2011 / 0279566, U.S. Patent Application Publication No. 2011 / 0279562, and U.S. Patent No. 9,180,676, the contents of which are incorporated herein by reference.

[0018] The first pinch valve 46 controls the flow of air through an air line 50 that branches off from the first incline 10. The air line 50 is open to atmosphere and, if desired, terminates in an air filter 52 which acts as an intake for the closed fluid loop.

[0019] The air tube 50 divides the first ink line 10 into a first portion 10a between the ink outlet port 106 and the air tube 50, and a second portion 10b between the printhead inlet port 8 and the air tube 50. A second pinch valve 48 controls the flow of ink through the first portion 10a of the first ink line 10.

[0020] The pump 40, the first pinch valve 46, and the second pinch valve 48 are controlled by a second controller 44 which coordinates the various fluid actuations. From the foregoing, it can be seen that the ink delivery system shown in FIG. 1 provides a wide variety of fluid actuations. Table 1 shows the states of the various pinch valves and pumps for some exemplary fluid actuations used in the printer 1. Of course, various combinations of these exemplary fluid actuations can be employed.

[0021] [Table 1]

[0022] During normal printing ("PRINT" mode), the printhead 4 draws ink from the intermediate ink tank 100 under gravity with a negative back pressure. In this mode, the peristaltic pump 40 acts as a shutoff valve while the first pinch valve 46 is closed and the second pinch valve 48 is open to allow ink flow from the ink outlet port 106 to the first port 8 of the printhead 4. When printing, ink is supplied to the ink inlet port 110 of the intermediate ink tank 100 under the control of the first controller 107 to maintain a relatively constant back pressure for the printhead 4.

[0023] When priming or flushing the printhead ("prime" mode), ink circulates in a forward direction (i.e., clockwise as shown in FIG. 1) through the closed fluid loop and the control valve 30 is closed. In this mode, the peristaltic pump 40 is driven in a pumping forward direction while the first pinch valve 46 is closed and the second pinch valve 48 is open to allow the flow of ink from the ink outlet port 106 through the printhead 4 to the ink return port 108. Priming can be used in this manner to prime the printhead with ink.

[0024] In "standby" mode, pump 40 is stopped while first pinch valve 46 is closed and second pinch valve 48 is open. "standby" mode maintains a negative static ink pressure at printhead 4, which minimizes color mixing on nozzle plate 19 when the printer is idle. Typically, the printhead is capped in this mode to minimize evaporation of ink from the nozzles (see, for example, U.S. Patent Application Publication No. 2011 / 0279519, the contents of which are incorporated herein by reference).

[0025] Before a used printhead 4 can be removed from the printer for replacement, it must be deprimed. In the "deprime" mode, the first pinch valve 46 is open, the second pinch valve 48 is closed, and the first pump 40 is driven forward to draw air from the atmosphere through the air line 50. After depriming the printhead 4, the printer is set to a "disable" mode which disconnects the printhead from the ink supply, allowing it to be safely removed with minimal ink spillage.

[0026] From the foregoing, it will be appreciated that a number of fluid operations may be performed using the ink delivery system described above in connection with FIG.

[0027] Priming Dry Printhead 4 The ink delivery system described in relation to Fig. 1 is well suited for priming wet printheads, i.e. printheads that are normally primed with transport fluid. In "prime" mode, the pump 40 is driven in a forward direction to draw ink into the printhead 4 through the inlet port 8. In this way, the transport fluid circulates clockwise through the ink delivery system, moving from the printhead 4 and back to the intermediate tank 100 via the second ink line 16 (dilution of the ink with the transport fluid is effectively unnoticeable by the user or is quickly mitigated by ejecting ink from the printhead 4).

[0028] However, dry printheads are not suitable for priming using the ink delivery system shown in FIG. 1 because driving the pump 40 in the forward direction tends to suck air into the printhead 4 through the ink ejection nozzles instead of drawing fresh ink into the printhead through the inlet port 8. The problem is particularly exacerbated in longer printheads, e.g., printheads longer than 200 mm or longer than 250 mm. One means of overcoming this problem in priming dry printheads is to seal the nozzles to prevent air from being sucked into the printhead 4. Printhead cappers are well known to those skilled in the art and are designed to inhibit dehydration of ink from the nozzles during idle periods (see, for example, the capper described in U.S. Pat. No. 10,518,536, the contents of which are incorporated herein by reference). However, cappers are unlikely to provide a perfect airtight seal around the printhead nozzle plate, especially in longer printheads. In fact, many cappers have small breather holes to equalize pressure inside and outside the capping chamber, allowing the printhead to be easily uncapped if necessary. Therefore, simply capping the printhead 4 is usually not an adequate solution to the problem of air being sucked into the nozzles when attempting to prime the printhead.

[0029] 2 shows a suitable system for priming a dry printhead 4. In this system, the printhead 4 is covered during priming by a capper 200. The capper 200 is further sucked down via a suitable vacuum source (e.g., a vacuum pump) connected to a capping chamber 202.

[0030] Thus, when the pump 40 drives forward in accordance with the "prime" operation described above, air cannot be sucked into the printhead 4 through the nozzles. Rather, a small vacuum pressure maintained within the capping chamber 202 of the capper 200 allows ink to be drawn into the printhead 4 through the inlet port 8, as desired, thereby priming the ink channels of the printhead with ink. The amount of suction is controlled to be sufficient to overcome the pressure exerted by the pump at the nozzles of the printhead. However, the amount of suction is controlled to be insufficient to draw ink into the capper 200 through the nozzles of the printhead. Thus, the ink channels of the printhead 4 interconnecting the inlet port 8 and the outlet port 14 can be primed with ink.

[0031] The second controller 44 may be used to control the amount of suction in the capping chamber 200 in cooperation with the actuation of the pump 40. In this manner, priming of the dry printhead can be achieved using a type of ink delivery system that does not rely on a forced unidirectional flow of ink through the printhead 4.

[0032] It will, of course, be understood that the invention has been described purely by way of example and modifications of detail are possible within the scope of the invention as defined in the appended claims.

Claims

1. 1. A system for priming a dry inkjet printhead, comprising: the ink jet printhead having an inlet port connected to an upstream ink line and an outlet port connected to a downstream ink line; a pump operably connected to the downstream incline; a capper engaged with the printhead; a vacuum source for applying suction to a capping chamber of the capper; a control system for regulating operation of the pump and the vacuum source; Equipped with In use, the pump is actuated simultaneously with the vacuum source, thereby drawing ink through the printhead from the inlet port to the outlet port to prime the printhead; the suction is insufficient to draw ink through the nozzles of the printhead; system.

2. 2. The system of claim 1, further comprising an ink tank, said upstream ink line and said downstream ink line connected to said ink tank to form a closed fluid loop with said printhead.

3. The system of claim 2 further comprising a bulk ink supply for refilling said ink tank.

4. The ink tank is adapted to control the ink pressure of the print head by gravity.

4. The system of claim 3, wherein the system is positioned below the level of the head.

5. The system of claim 1 , wherein the pump is a one-way pump.

6. The system of claim 5 , wherein the pump is an in-line peristaltic pump.

7. The suction is applied by the pump at the nozzles of the print head. The system of claim 1 , wherein the pressure is sufficient to overcome the pressure.

8. A method of priming a dry inkjet printhead using a system according to any one of claims 1 to 7.

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