Ink tank with built-in filter

Abstract

An ink tank for an ink delivery system includes a housing having an ink inlet port and an ink outlet port, a vent port communicating with a headspace of the ink tank, a filter disposed within the housing for filtering ink supplied from the ink tank through the ink outlet port, and a baffle plate disposed within the housing between the ink inlet port and the filter. The baffle plate is configured to direct air bubbles entering the ink tank through the ink inlet port toward the headspace of the ink tank. A baffle opening is disposed toward a base of the ink tank, thereby allowing ink to flow from the ink inlet port through the baffle opening toward the ink outlet port.

Description

[Technical field]

[0001] The present invention relates to an ink tank having an integral filter for an ink delivery system of an ink jet printer, which was developed primarily to minimize problems associated with air bubbles in the ink delivery system. [Background technology]

[0002] Inkjet printers employing Memjet® technology are commercially available for many different printing formats, including small office home office ("SOHO") printers, label printers, digital inkjet presses, and wide format printers. Memjet® printers typically include one or more fixed, user-replaceable inkjet printheads. For example, desktop printers include a single user-replaceable multicolor or monochrome printhead, high-speed digital presses include multiple user-replaceable monochrome printheads aligned along the media feed direction, and wide format printers include multiple user-replaceable printheads arranged in a staggered fashion to span the width of a wide format page.

[0003] Ink is supplied to the inkjet printhead through an ink delivery system that is primarily designed to deliver the ink to the printhead at a given hydrostatic pressure, and the ink delivery system typically also includes an ink filter to filter particles from the ink.

[0004] Air bubbles are a constant problem in inkjet printers. Air bubbles that reach the inkjet nozzles can block the nozzles and cause a catastrophic depriming event. Air bubbles can also reduce the effectiveness of ink filters in the ink delivery system by blocking the fine pores in the filter material. Air bubbles can also affect the operation of ink level sensors, for example by sticking to float sensors, increasing buoyancy, which can cause erroneous ink level readings.

[0005] Problems associated with air bubbles can be mitigated to some extent by using degassed ink in a sealed ink delivery system. However, such ink delivery systems are not immune to the problem of air bubbles, even when degassed ink is used. For example, air is intentionally introduced into the ink delivery system by the printhead depriming operation when air is drawn through the printhead, allowing the printhead to be replaced with minimal ink contamination. This introduced air can circulate around the ink delivery system and cause problems such as clogging the ink filters. If the ink filters become catastrophically clogged with air bubbles, they must be replaced by the user, which is inconvenient and time consuming.

[0006] In some ink delivery systems described in the prior art, the ink filter is connected to a degassing pump that removes air from a filter chamber that contains a filter material. The degassing pump ensures that air bubbles trapped in the ink filter can escape to the atmosphere without causing long-term problems due to continued accumulation of air bubbles. However, the degassing pump increases the cost and complexity of the ink delivery system.

[0007] WO2019 / 011705 describes an ink filter that passively degass under positive ink pressure via a ventilated tube.

[0008] It would therefore be desirable to provide an ink tank having an integral filter that minimizes the ingress of air bubbles into the filter. It would further be desirable to provide an ink tank that can efficiently remove air bubbles. It would further be desirable to provide an ink tank having an ink level sensor whose operation is not affected by air bubbles in the ink. Summary of the Invention

[0009] In a first aspect, there is provided an ink tank for an ink delivery system, the ink tank comprising: a housing having an ink inlet port and an ink outlet port; a vent hole communicating with a head space of the ink tank; a filter disposed within the housing for filtering ink supplied from the ink tank through the ink outlet port; a baffle plate disposed within the housing between the ink inlet port and the filter, the baffle plate configured to direct air bubbles entering the ink tank through the ink inlet port toward the headspace of the ink tank; Including, The baffle plate has a baffle opening disposed toward a base of the ink tank, thereby allowing ink to flow from the ink inlet port through the baffle opening toward the ink outlet port.

[0010] Preferably, the ink tank comprises an upper section and a lower section, said lower section having said ink inlet port and said ink outlet port.

[0011] Preferably, the upper section is more voluminous than said lower section.

[0012] Preferably, the upper section has a larger cross-sectional area than said lower section.

[0013] Preferably, an ink outlet port is located in a base of said housing and said filter includes a filter drum located above said ink outlet port.

[0014] Preferably, a baffle plate extends from the base of the housing towards the roof of the ink tank.

[0015] Preferably, in use, the baffle plate extends into a headspace of the ink tank.

[0016] Preferably, the ink inlet port is located above said baffle opening.

[0017] Preferably, the ink tank further comprises an ink level sensor, and said baffle plate is disposed between said ink level sensor and said ink inlet port.

[0018] Preferably, the ink level sensor comprises a float level sensor having a stem extending into said ink tank and one or more floats movable along said stem.

[0019] Preferably, the vent communicates with a labyrinth channel defined in the roof of said ink tank.

[0020] In a second aspect, an ink delivery system is provided, the ink delivery system comprising: The ink tank and an ink supply reservoir connected to the ink inlet port via an ink supply line; an inkjet printhead having a printhead inlet port connected to said ink outlet port via an ink delivery line; a control system operatively associated with the ink tank for controlling the hydrostatic pressure of ink delivered to the printhead; Equipped with.

[0021] Preferably, the printhead includes a printhead outlet port in fluid communication with said ink tank via an ink return line.

[0022] Preferably, an ink return line is connected to the ink supply line.

[0023] Preferably, the ink delivery system further comprises a pump and an air intake for depriming the printhead.

[0024] Preferably, during printhead depriming and / or printhead priming, air enters the ink tank through the ink inlet port.

[0025] Preferably, the control system is arranged to control the level of ink in said ink tank.

[0026] Preferably, the control system controls a supply pump in the ink supply line in response to feedback from one or more ink level sensors in the ink tank.

[0027] The term "ink" as used herein is intended to mean any printing fluid that can be printed from an inkjet printhead. Inks may or may not contain colorants. Thus, the term "ink" includes traditional dye-based or pigment-based inks, infrared inks, UV inks, fixatives (e.g., precoats, primers, finishers, etc.), 3D printing fluids, biological fluids, functional printing fluids (e.g., solar inks, biosensing inks, etc.), and the like.

[0028] As used herein, the term "printer" refers to any printing device, such as a traditional desktop printer, a label printer, a duplicator, a copier, a digital inkjet press, a 3D printer, etc. A printer may be, for example, a sheet-fed or a web-fed printing device. [Brief description of the drawings]

[0029] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0030] [Figure 1] FIG. 1 shows diagrammatically the ink delivery system of a printer incorporating an ink tank according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view of an ink tank according to the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of the ink tank shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Gravity-fed ink supply system As one exemplary use of the ink tank according to the first aspect, a gravity-fed ink delivery system is described below, however, it should be noted that the ink tank according to the first aspect is equally suitable for use in a recirculating ink delivery system incorporating an ink filter.

[0032] 1, there is shown generally a printer 1 having an ink delivery system for supplying ink to a printhead 4. The ink delivery system is a gravity-fed system and is similar in function to those described in US2011 / 0279566 and US2011 / 0279562, the contents of which are incorporated herein by reference.

[0033] The ink delivery system comprises an ink tank 100 having an ink outlet port 106 connected to a printhead inlet port 8 of the printhead 4 via a first ink delivery line 10. An ink inlet port 108 of the ink tank 100 is connected to a printhead outlet 14 of the printhead 4 via an ink return line 16. Thus, the ink tank 100, the ink delivery line 10, the printhead 4, and the ink return line 16 together form a closed fluid loop. Typically, the ink delivery line 10 and the ink return 16 are constructed from lengths of flexible tubing that are the same or different diameters. In some embodiments, the ink return line 16 has a smaller diameter than the ink delivery line 10 for efficient bubble removal, as described in EP2844488B and US2014 / 0015905, the contents of which are incorporated herein by reference.

[0034] The ink tank 100 further includes an integral filter 112 disposed over the ink outlet port 106 for filtering ink supplied to the printhead 4, and a baffle plate 114 disposed between the ink inlet port 108 and the filter 112. The function of the baffle plate 114 will be described in more detail below.

[0035] The printhead 4 is user replaceable by a first coupling 3 that releasably interconnects a printhead inlet port 8 with a first ink line 10, and a second coupling 5 that releasably interconnects a printhead outlet port 14 with a second ink line 16. The printhead 4 is typically a pagewidth printhead, such as those described in U.S. Pat. No. 10,399,354 or U.S. Pat. No. 10,293,609, the contents of which are incorporated herein by reference.

[0036] The ink 20 contained in the ink tank 100 is open to the atmosphere through a vent hole 109 located in the roof of the ink tank. Thus, during normal printing, ink is supplied to the printhead 4 at a negative hydrostatic pressure under the force of gravity ("back pressure"). In other words, the gravity supply of ink from the ink tank 100 located below the printhead 4 provides a pressure regulation system for supplying ink to the printhead at a predetermined negative hydrostatic pressure. The amount of back pressure experienced by the nozzle plate 19 of the printhead 4 is determined by the height h of the nozzle plate relative to the level of ink 20 in the ink tank 100.

[0037] Ink is supplied to the ink inlet port 108 of the ink tank 100 from a bulk ink reservoir comprising a collapsible ink bag 23 housed by an ink cartridge 24. The ink cartridge 24 is open to the atmosphere via a cartridge vent 25 so that the collapsible ink bag 23 collapses as ink is consumed by the system. The collapsible ink bag 23 is typically an air-impermeable foil bag containing degassed ink that is supplied to the ink inlet port 108 via an ink supply line 28 connected to an ink return line 16. The ink cartridge 24 is typically user replaceable and is connected to the ink supply line 28 via a suitable ink supply coupling 32. The ink supply line 28 includes an in-line ink filter (not shown) for filtering the ink before it reaches the ink tank 100.

[0038] A control system is used to maintain the level of ink in the ink tank 100 substantially constant, thus maintaining a constant height h and corresponding back pressure. As shown in FIG. 1, a supply pump 30 is disposed in the ink supply line 28 and controls the flow of ink from the cartridge 24 to the ink tank 100. The supply pump 30 operates under the control of a first controller 107, which receives feedback from an ink level sensor 120 having "high" and "low" float sensors 102 and 104 (e.g., magnetic float sensors) disposed in the ink tank 100. When the level of ink 20 falls below the "low" sensor 104, the first controller 107 signals the supply pump 30 to pump ink into the ink tank 100, and when the level of ink reaches the "high" sensor 102, the first controller signals the supply pump to stop pumping. In this manner, the level of ink 20 in the ink tank 100 can be maintained relatively constant.

[0039] A closed fluid loop incorporating the ink tank 100, ink delivery line 10, printhead 4 and ink return line 16 facilitates priming, depriming and other necessary fluid operations. The ink return line 16 includes a reversible peristaltic pump 40 for circulating ink around the fluid loop. As a matter of convention only, the "forward" direction of the pump 40 corresponds to pumping ink from the ink outlet port 106 to the return port 108 (i.e., clockwise as shown in FIG. 1 ) and the "reverse" direction of the pump corresponds to pumping ink from the return port 108 to the ink outlet port 106 (i.e., counterclockwise as shown in FIG. 1 ).

[0040] The pump 40 cooperates with a pinch valve arrangement 42 to regulate various fluid operations. 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 US 2011 / 0279566, US 2011 / 0279562 and US 9180676, the contents of which are incorporated herein by reference.

[0041] A first pinch valve 46 controls the flow of air through an air conduit 50, which branches off from the ink delivery line 10. The air conduit 50 is open to the atmosphere and terminates in an air filter 52 which serves as an air intake for the closed fluid loop.

[0042] The air conduit 50 divides the ink delivery line 10 into a first section 10a between the ink outlet port 106 and the air conduit 50 and a second section 10b between the printhead inlet port 8 and the air conduit 50. A second pinch valve 48 controls the flow of ink through the first section 10a of the ink delivery line 10.

[0043] The pump 40, first pinch valve 46, and second pinch valve 48 are controlled by a second controller 44 which coordinates the various fluid operations. From the foregoing, it will be appreciated that the ink delivery system shown in FIG. 1 provides a versatile range of fluid operations. Table 1 describes the states of the various pinch valves and pumps for several example fluid operations used in printer 1. Of course, various combinations of these example fluid operations can be used. TIFF0007656623000001.tif89170

[0044] During normal printing ("PRINT" mode), the printhead 4 draws ink from the ink tank 100 with negative back pressure due to gravity. In this mode, the peristaltic pump 40 is either pumping ink forward around the fluid loop or switched off and acting as a shutoff valve. The first pinch valve 46 is closed and the second pinch valve 48 is opened to allow ink flow from the ink outlet port 106 to the printhead inlet port 8. During printing, ink is supplied to the ink inlet port 108 of the ink tank 100 under the control of the first controller 107 to maintain the ink level 20 relatively constant, and therefore the back pressure of the printhead 4, relatively constant.

[0045] During priming or flushing of the printhead ("PRIME" mode), ink is circulated in a forward direction (i.e., clockwise in FIG. 1 ) around the closed fluid loop with the supply pump turned off. In this mode, the peristaltic pump 40 operates in a forward pumping direction while the first pinch valve 46 closes and the second pinch valve 48 opens to allow ink flow through the printhead 4 from the ink outlet port 106 to the ink inlet port 108. Priming in this manner can be used to prime an unprimed printhead with ink, flush air bubbles from the printhead 4, and / or filter particles from the ink.

[0046] In the "STANDBY" mode, the pump 40 is switched off while the first pinch valve 46 is closed and the second pinch valve 48 is open. Typically, the printhead is capped in the standby mode to minimize evaporation of ink from the nozzles (see, for example, US2011 / 0279519, the contents of which are incorporated herein by reference).

[0047] To ensure that each nozzle of the printhead 4 is fully primed with ink and / or to unclog clogged nozzles, a "pulse" mode can be used. In the "pulse" mode, the first and second pinch valves 46 and 48 are closed while the pump 40 is actuated in the reverse direction (i.e., counterclockwise in FIG. 1 ) to force ink out of the nozzles of the nozzle plate 19 of the printhead 4. During pulse priming, the supply pump 30 is off and the ink tank 100 provides a reservoir of ink necessary for pulse priming. Alternatively, the nozzles may be primed using external suction at the nozzle plate 19, for example, as described in U.S. Provisional Application No. 62 / 976,213, filed February 13, 2020 ("Method and System for Priming a Dry Printhead"), which is incorporated herein by reference.

[0048] To replace a used printhead 4, the printhead must be deprimed before it is removed from the printer. In "depriming" mode, the first pinch valve 46 opens, the second pinch valve 48 closes, and the first pump 40 operates in a forward direction to draw air from the atmosphere through the air conduit 50. Depriming replaces the ink in the printhead 4 with air and introduces air bubbles into the ink tank 100 through the ink inlet port 108. Once the printhead 4 is cleared of ink, the printer is set to "NULL" mode, isolating the printhead from the ink supply so that it can be safely removed with minimal ink spillage.

[0049] Ink tank 100 In a recirculating ink delivery system using degassed ink, introducing air into the system for de-priming and replacement of printheads is potentially problematic. This is problematic because dissolved air can outgas within the printhead, potentially eliminating the inherent benefits of using degassed ink. Additionally, undissolved air bubbles can behave similarly to particulates and clog the ink delivery system. Ideally, undissolved air bubbles should be removed from the system before they cause problems such as clogging the printhead 4 nozzles or plugging the ink filters.

[0050] 2 and 3, the ink tank 100 is designed to facilitate pressure regulation, ink circulation, filtration, and removal of air bubbles from the ink delivery system. The ink tank 100 includes a housing 200, typically formed of molded plastic, that defines an upper section 202 and a lower section 204 of the ink tank.

[0051] The lower section 204 includes a truncated cylindrical portion 205 that houses the filter 112, which takes the form of a cylindrical filter drum 113. The filter drum 113 is positioned at the base of the housing 200 above the ink outlet port 106 and delivers filtered ink to the printhead 4.

[0052] The ink inlet port 108 is located in the side wall of the lower section 204 so that all ink entering the ink tank 100 through the ink inlet port is filtered by the filter 112 before exiting the ink tank through the ink outlet port 106. (An additional connection port 207, capped in Figures 2 and 3, is provided for the option of fluidly connecting multiple ink tanks 100 together if desired).

[0053] A lid 206 is secured to the top of the housing 200 to define a roof for the ink tank 100. The lid 206 defines a vent 109 that communicates with the headspace of the ink tank 100 and a labyrinth channel 208 connected to the vent. A vent port 210 open to the atmosphere extends downwardly from the lid 206 and communicates with the headspace of the ink tank 100 via the labyrinth channel 208 and the vent 109. The labyrinth channel 208 functions to minimize evaporation of water from the ink tank 100 while allowing air to be vented therethrough.

[0054] The baffle plate 114 extends upward from the bottom of the ink tank 100 toward the lid 206 and is disposed between the ink inlet port 108 and the filter 112. Typically, the baffle plate 114 is an insert that is slidably received within the molded housing 200. The baffle plate 114 effectively divides the ink tank 100 into a first side 209 having the ink inlet port 108 and a second side 210 having the filter 112 and ink outlet port 106.

[0055] The lower portion of the baffle plate 114 defines a baffle opening 212 that allows the passage of ink from the ink inlet port 108 on the first side 209 through the lower section 204 of the ink tank 100 toward the filter 112 on the second side 210. The ink inlet port 108 is positioned above the baffle opening 212 such that air bubbles entering the ink tank 100 through the ink inlet port do not pass through the baffle opening and enter the second side 210 of the ink tank 100. Instead, air bubbles entrained in the ink pumped into the ink tank through the ink inlet port 108 tend to strike the baffle plate 114 above the baffle opening 212 and float upward into the headspace of the ink tank where they can be vented to the atmosphere through the vent 109. The baffle plate 114 thus protects the filter 112 from air bubbles entering the ink tank 100 through the ink inlet port 108 (as long as a minimum number of air bubbles reach the filter 112, the air bubbles can float upward toward the vent). The baffle plate 114 also protects the float sensors 102 and 104 from air bubbles, as will be further explained below.

[0056] When fresh degassed ink from the ink tank enters the ink tank 100 through the ink inlet port 108, the ink flows through the baffle opening 212 and through the lower section 204 of the ink tank towards the filter 122. The baffle plate 114 extends into the headspace of the ink tank 100 and prevents the ink contained in the upper section 202 from passing from the first side 209 to the second side 210 of the ink tank. Because the vented ink in the upper section 202 is relatively stationary and separated (in height) from the ink in the lower section 204, the vented ink diffuses towards the lower section 204 only very slowly. Thus, during normal printing, the degassed ink in the lower section 204 remains degassed as fresh degassed ink is replenished from the ink reservoir. The design of the ink tank 100 thus provides an effective diffusion barrier between the upper section 202 and the lower section 204, allowing for the use of degassed ink whilst being suitable for gravitational control of back pressure at the printhead 4.

[0057] The ink level sensor 120 takes the form of a magnetic float sensor fixed to the lid 206 and having a stem 222 that extends into the ink tank 100. The "high" and "low" float sensors 102 and 104 are movable along the stem 222 between respective fixed stops 224. Each float sensor includes a magnet that activates a respective reed switch (not shown) in the stem 222 to indicate a "high" or "low" level of ink in the ink tank 100. As described above, the supply pump 30 is activated or deactivated depending on the level of the float sensors 102 and 104 and the corresponding state of the reed switch. The ink level sensor 120 is located on the second side of the ink tank 100 and is thereby protected from air bubbles by the baffle plate 114. Protecting the float sensors 102 and 104 from air bubbles advantageously minimizes erroneous ink level signals from the ink level sensor 109 by avoiding disturbances to the sensitive float sensors.

[0058] From the above, it will be appreciated that the ink tank 100 accomplishes multiple functions: (1) protecting the filter from air bubbles, (2) protecting the ink level sensor from air bubbles, (3) efficiently removing air bubbles from the ink delivery system, and (4) gravity control of ink pressure in an ink delivery system supplied with degassed ink. These and other advantages will be readily apparent to those skilled in the art.

[0059] It should of course be noted 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. An ink tank for an ink delivery system, comprising: a housing having an ink inlet port and an ink outlet port; a vent hole communicating with a head space of the ink tank; a filter disposed within the housing for filtering ink supplied from the ink tank through the ink outlet port; a baffle plate disposed within the housing between the ink inlet port and the filter, the baffle plate configured to direct air bubbles entering the ink tank through the ink inlet port toward the headspace of the ink tank; Including, the baffle plate has a baffle opening disposed toward a base of the ink tank to allow ink to flow from the ink inlet port through the baffle opening toward the ink outlet port; 11. An ink tank according to claim 10, wherein the ink outlet port is disposed in a base of the housing, and the filter includes a filter drum disposed over the ink outlet port.

2. 2. The ink tank according to claim 1, 13. The ink tank according to claim 12, wherein said ink tank comprises an upper section and a lower section, said lower section having said ink inlet port and said ink outlet port.

3. 3. The ink tank according to claim 2, An ink tank, wherein the upper section has a larger volume than the lower section.

4. 3. The ink tank according to claim 2, 10. An ink tank comprising: an upper section having a larger cross-sectional area than said lower section;

5. 2. The ink tank according to claim 1, The baffle plate extends from the base of the housing toward a roof of the ink tank.

6. 2. The ink tank according to claim 1, In use, the baffle plate extends into a headspace of the ink tank.

7. 2. The ink tank according to claim 1, The ink tank according to claim 1, wherein the ink inlet port is disposed above the baffle opening.

8. 2. The ink tank according to claim 1, further comprising:

13. An ink tank comprising: an ink level sensor; and wherein the baffle plate is disposed between the ink level sensor and the ink inlet port.

9. 9. The ink tank according to claim 8, 11. An ink tank according to claim 10, wherein the ink level sensor comprises a float level sensor having a stem extending into the ink tank and one or more floats movable along the stem.

10. 2. The ink tank according to claim 1, 11. An ink tank, comprising: an ink tank having a roof, the ink tank being adapted to receive a vent hole;

11. 1. An ink delivery system for an inkjet printer, comprising: The ink tank according to claim 1 , an ink supply reservoir connected to the ink inlet port via an ink supply line; an inkjet printhead having a printhead inlet port connected to said ink outlet port via an ink delivery line; a control system operatively associated with the ink tank for controlling the hydrostatic pressure of ink delivered to the printhead; 1. An ink delivery system comprising:

12. 12. The ink delivery system of claim 11, The ink delivery system of claim 1, wherein the printhead includes a printhead outlet port in fluid communication with the ink tank via an ink return line.

13. 13. The ink delivery system of claim 12, wherein the ink return line is connected to the ink supply line.

14. 13. The ink delivery system of claim 12, The ink delivery system further comprising a pump and an air intake for depriming the printhead.

15. 15. The ink delivery system of claim 14, 11. An ink delivery system, comprising: a printhead having a first ink supply port and a second ink supply port; a printhead having a second ink supply port; and a printhead having a second ink supply port.

16. 12. The ink delivery system of claim 11, wherein the control system is configured to control the level of ink in the ink tank.

17. 17. The ink delivery system of claim 16, An ink delivery system, wherein the control system controls a supply pump in the ink supply line in response to feedback from one or more ink level sensors in an ink tank.

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