Low cost ink delivery system for controlling ink pressure

Abstract

An ink delivery system for delivering ink to an inkjet printhead. The system includes a first ink tank, a second ink tank, a main air line having an air inlet and an air outlet, a first air line interconnecting the first ink tank with the main air line, a second air line interconnecting the second ink tank with the main air line, an air pump positioned in the main air line, a first air flow restrictor and a second air flow restrictor positioned in the main air line, an ink circulation line interconnecting the first ink tank with the second ink tank, and an ink pump positioned in the ink circulation line to pump ink from the first ink tank to the second ink tank.

Description

Technical Field

[0001] This invention relates to an ink delivery system for an inkjet printer. The ink delivery system is primarily developed to supply ink to one or more printheads under relatively constant pressure and to reduce the cost of existing circulating ink delivery systems. Background Technology

[0002] Memjet ® Memjet's inkjet printers are commercially available for many different printing formats, including home office (“SOHO”) printers, label printers, and wide-format printers. ® Printers typically include one or more fixed inkjet printheads that are user-replaceable. For example, SOHO printers include a single user-replaceable multicolor printhead, high-speed inkjet printers include multiple user-replaceable monochrome printheads aligned along the media feed direction, and wide-format printers include multiple user-replaceable printheads arranged in an overlapping manner to span the width of a wide page.

[0003] As the number of printheads increases, supplying ink to multiple printheads can become problematic. To maintain high print quality, each printhead should receive ink from a shared ink reservoir at approximately the same ink pressure.

[0004] US 10,252,540 describes an ink delivery system suitable for use in a digital inkjet printer with multiple printheads in the same color channel, the contents of which are incorporated herein by reference. This system uses overall pressure control in a shared ink delivery module and local fine pressure control in each printing module containing the respective printheads. Due to the high ink flow requirements of multiple inkjet printheads, the diaphragm pump used to control the ink pressure in the ink delivery module must be a large, high-quality pump. Consequently, the ink delivery module is necessarily the most expensive component in the entire ink delivery system, primarily due to the higher cost of the diaphragm pump.

[0005] For inkjet printers with a few (e.g., one or two) print modules in each color channel, designing expensive ink delivery modules for larger systems is undesirable and significantly increases the total cost of the system. Therefore, it is desirable to provide a low-cost ink delivery system suitable for smaller inkjet printers. Furthermore, it is desirable to provide a low-cost alternative to the ink delivery module described in US 10,252,540. Summary of the Invention

[0006] In a first aspect, an ink delivery system is provided for delivering ink to one or more printheads, the system comprising:

[0007] The first ink tank has a first air port, a first ink port for connecting to the printhead outlet, an ink filling port for connecting to a bulk ink supply source, and a first ink circulation port.

[0008] The second ink tank has a second air port, a second ink port for connecting to the printhead inlet, and a second ink circulation port;

[0009] Main air duct with air inlet and air outlet;

[0010] The first air line that connects the first air port to the main air line;

[0011] A second air line that interconnects the second air port with the main air line;

[0012] An air pump located in the main air line between the first air line and the second air line, the air pump being configured to pump air from the air inlet toward the air outlet;

[0013] A first airflow limiter is positioned between the air inlet and the first air line;

[0014] A second airflow limiter is positioned between the air outlet and the second air line;

[0015] Ink circulation lines connecting the first and second ink tanks; and

[0016] An ink pump is positioned in the ink circulation line to pump ink from the first ink tank to the second ink tank.

[0017] The ink delivery system according to the first aspect advantageously utilizes a single, low-cost air pump in conjunction with an airflow limiter to control the ink pressure in both the low-pressure and high-pressure ink tanks. This ink delivery system is particularly suitable for inkjet printer types with one or two monochrome printheads in each color channel. In this way, a stable pressure can be delivered to (multiple) printheads without the need for expensive, high-quality diaphragm pumps.

[0018] Preferably, the first ink tank is under negative pressure, and the second ink tank is under positive pressure.

[0019] Preferably, the negative ink line is connected to the first ink port, the positive ink line is connected to the second ink port, and one or more printheads are interconnected between the positive ink line and the negative ink line.

[0020] Preferably, each printhead is contained in a printing module with local pressure control.

[0021] Preferably, the ink delivery system further includes a bulk ink supply source connected to the first ink tank via an ink supply line.

[0022] Preferably, the ink delivery system further includes a filling pump positioned in the ink supply line.

[0023] Preferably, the first ink can has a first ink height sensor, and the filling pump is controlled to pump ink from the bulk ink supply source to the first ink can in response to the first ink height sensor sensing a predetermined ink height in the first ink can.

[0024] Preferably, the second ink tank has a second ink height sensor, and the ink pump is controlled to pump ink from the first ink tank to the second ink tank in response to the second ink height sensor sensing a predetermined ink height in the second ink tank.

[0025] Preferably, the ink delivery system is configured to circulate ink from a second ink tank through one or more printheads and return ink to a first ink tank.

[0026] In a second aspect, a method is provided for controlling a first ink pressure and a second ink pressure in corresponding first ink tanks and second ink tanks, the first ink tank and the second ink tank having corresponding first air lines and second air lines connected to a main air line, the method comprising the following steps:

[0027] An air pump operably connected to the main air line between the first air line and the second air line; and

[0028] The first and second ink pressures are controlled using a first airflow restrictor and a second airflow restrictor located in the main air line.

[0029] The first airflow limiter is located upstream of the first airflow line, and the second airflow limiter is located downstream of the second airflow line, relative to the airflow direction passing through the main airflow line.

[0030] Preferably, the first airflow limiter and the second airflow limiter are adjustable.

[0031] Preferably, the first airflow limiter and the second airflow limiter can be controlled independently.

[0032] Preferably, the first ink tank and the second ink tank are connected in a fluid circuit containing one or more inkjet printheads.

[0033] Preferably, the method includes a step of printing from a printhead.

[0034] Preferably, the method includes a step of locally controlling the ink pressure in each printhead during printing.

[0035] Preferably, the method includes the step of replenishing the ink in the second ink tank by pumping ink from the first ink tank to the second ink tank.

[0036] Preferably, the method includes the step of replenishing the ink in the first ink tank by pumping ink from a bulk ink supply source to the first ink tank.

[0037] Preferably, the first ink tank is under negative pressure, and the second ink tank is under positive pressure.

[0038] As used herein, the term "ink" is considered to refer to any printing fluid that can be printed from an inkjet printhead. Ink may or may not contain colorants. Therefore, the term "ink" can include conventional dye-based or pigment-based inks, infrared inks, fixing agents (such as pre-coatings and finishing agents), 3D printing fluids, etc. In the context of reference to fluids or printing fluids, this is not intended to limit the meaning of "ink" as used herein. Attached Figure Description

[0039] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0040] Figure 1 The ink delivery system according to the present invention is illustrated schematically; and

[0041] Figure 2 This is a 3D view of the printing module. Detailed Implementation

[0042] refer to Figure 1 The diagram schematically illustrates an ink delivery system 1, which includes a positive ink line 3 (“positive rail”) and a negative ink line 5 (“negative rail”) connected to ink delivery modules 7. This system regulates the ink pressure in each of the positive and negative ink lines. Multiple printing modules 9 are interconnected between the positive ink line 3 and the negative ink line 5 via corresponding inlet lines 10 and outlet lines 12. Although... Figure 1 Two print modules 9 are shown, but it should be understood that any number of print modules (e.g., 1, 2, or 3 print modules) can be interconnected between the positive ink line 3 and the negative ink line 5. The print modules 9 can be physically positioned in a staggered, overlapping arrangement to extend across a wider area of ​​the printing medium than a single print module can. In this way, multiple print modules 9 can be used to print on media wider than approximately 8 inches (e.g., at least 16 inches, at least 32 inches, or at least 40 inches). Alternatively or additionally, the print modules 9 can be aligned along the media feed path.

[0043] Brief Reference Figure 2A single printing module 9 includes a supply module 14 and a printhead 16 releasably connected to the supply module. The printhead 16 contains an array of print chips for inkjet printing on a printing medium and can be a monochrome or color printhead (e.g., a two-color or four-color printhead), as known in the art. For example, the printhead 16 can be of the type described in US 9,950,527, the contents of which are incorporated herein by reference. For clarity, an ink delivery system for a single color of ink is described herein; however, it should be understood that multiple ink delivery systems can be used to supply multiple colors of ink.

[0044] The supply module 14 includes a body 20 housing the drive and logic circuitry system for the printhead 16 (e.g., one or more PCBs with a print engine controller chip, drive transistors, etc.), an inlet module 22, and an outlet module 24. The inlet module 22 has a module inlet port 26 connected to the inlet line 10, and the outlet module 24 has a module outlet port 28 connected to the outlet line 12. A suitable print module connector 29 allows for easy replacement of the entire print module when needed.

[0045] The printhead 16 is fluidly connected to the supply module 14 via the printhead inlet connector 30 and the printhead outlet connector 32. The printhead inlet connector 30 and the printhead outlet connector 32 are typically quick-connect connectors, allowing the user to easily remove the depleted printhead 16 from each print module 9 and replace it with a new printhead.

[0046] The inlet module 22 contains all the necessary components for providing local control of the ink pressure in the printhead 16 of the corresponding print module 9. Therefore, each print module 9 provides local, independent control of the ink pressure in its respective printhead 16, enabling automatic and dynamic fine-tuning of the local ink pressure in response to local pressure fluctuations. For a detailed description of the local pressure control within each print module 9, see US 10,252,540, the contents of which are incorporated herein by reference.

[0047] return Figure 1The ink delivery module 7 includes a first ink tank 50 and a second ink tank 54. The first ink tank has a first ink port 52 connected to a negative ink line 5, and the second ink tank has a second ink port 56 connected to a positive ink line 3. The first ink tank 50 and the second ink tank 54 have corresponding first air ports 58 and 60 connected to a common main air line 62 via corresponding first air lines 64 and 66. An air pump 68 is positioned in the main air line 62 between the first air line 64 and the second air line 66. The air pump 68 draws air in through an air inlet 70 at one end of the main air line 62 and pumps air out through an air outlet 72 at the opposite end. A first (upstream) airflow restrictor 76 is positioned between the air inlet 70 and the first air line 64, while a second (downstream) airflow restrictor 78 is positioned between the air outlet 72 and the second air line 66. The first airflow limiter 76 and the second airflow limiter 78 can be adjusted independently to independently control the airflow passing through them. In some embodiments, the first airflow limiter 76 and the second airflow limiter 78 can be automatically adjusted under the control of a controller (not shown) to dynamically adjust the ink pressure in response to an air or ink pressure sensor (not shown) in the first ink tank 50 and the second ink tank 54.

[0048] When the air pump 68 is actuated, the first airflow restrictor 76 and the second airflow restrictor 78 cooperate to generate a negative pressure at the top in the first ink tank 50 and a positive pressure at the top in the second ink tank 54. During printing, ink is drawn from the second ink tank 54 via the positive ink line 3, passes through the multiple printing modules 9 containing respective printheads(s)16, and returns to the first ink tank 50 via the negative ink line 5.

[0049] Ink consumed by the second ink tank 54 is replenished from the first ink tank 50 via an ink circulation line 80, which interconnects the first ink circulation port 82 of the first ink tank and the second circulation port 84 of the second ink tank. An ink pump 86 (or "lift pump") is positioned in the ink circulation line 80 to lift ink from the negatively pressurized first ink tank 50 to the positively pressurized second ink tank 54. Actuation of the ink pump 86 is controlled by a controller (not shown) that receives a signal from a second ink level sensor 88 in the second ink tank 54 and actuates the pump in response to the ink level in the second ink tank falling below a predetermined height.

[0050] The first ink tank 50 is replenished from a bulk ink supply source 90 via a supply line 92, which interconnects the bulk ink supply source with the filling port 94 of the first ink tank. A filling pump 96 is positioned in the supply line 92 to refill the first ink tank 50 when the ink in the first ink tank is depleted. Actuation of the filling pump 96 is controlled by a controller (not shown) that receives a signal from a first ink level sensor 98 in the first ink tank 50 and actuates the filling pump in response to the ink level in the first ink tank dropping below a predetermined height.

[0051] The ink delivery module 7 is typically a separate unit having several different external connectors: a supply connector 101 for connecting to the supply line 92; a positive line connector 102 for connecting to the positive ink line 3; and a negative line connector 103 for connecting to the negative ink line 5.

[0052] As described above, during printing, ink is supplied to the positive ink line 3 under regulated positive pressure. Each print module 9 draws ink from the positive ink line 3, and the ink is fed back to the ink delivery module 7 via the negative ink line 5 under regulated negative pressure. By maintaining control over the relative positive and negative pressures in the positive and negative ink lines 3 and 5, a relatively constant back pressure is provided at each print module 9. Additional local control of the back pressure in each printhead 16 can be provided by a local pressure controller in each print module 9 (see US 10,252,540).

[0053] Air pump 68 controls the top pressure in both the first ink tank 50 and the second ink tank 54 via a first airflow restrictor 76 and a second airflow restrictor 78. This air pump advantageously enables simple pressure control without the need for an expensive, high-quality diaphragm pump in the ink delivery module 7. The lift pump 86 is likely a relatively inexpensive pump because it does not involve pressure regulation. Accordingly, the total cost of the ink delivery module 7 is minimized compared to prior art systems, while still providing adequate pressure control for, for example, one or two printing modules 9.

[0054] Of course, it should be understood that the invention has been described by way of example only, and modifications to the details may be made within the scope of the invention as defined in the appended claims.

Claims

1. An ink delivery system for delivering ink to one or more inkjet printheads, the system comprising: - A first ink tank, the first ink tank having a first air port, a first ink port for connecting to the printhead outlet, an ink filling port for connecting to a bulk ink supply source, and a first ink circulation port; - A second ink tank, the second ink tank having a second air port, a second ink port for connecting to the printhead inlet, and a second ink circulation port; - Main air duct with air inlet and air outlet; - A first air line that interconnects the first air port with the main air line; - A second air line that interconnects the second air port with the main air line; - An air pump located in the main air line between the first air line and the second air line, the air pump being configured to pump air from the air inlet toward the air outlet during printing; - A first airflow restrictor positioned between the air inlet and the first air line; - A second airflow restrictor positioned between the air outlet and the second air line; - An ink circulation line that connects the first ink tank and the second ink tank; - An ink pump positioned in the ink circulation line to pump ink from the first ink tank to the second ink tank. And it is characterized by: - A controller configured to adjust the first airflow restrictor and the second airflow restrictor during printing, thereby controlling the first ink pressure and the second ink pressure in the first ink tank and the second ink tank.

2. The ink delivery system as described in claim 1, wherein, The first ink tank is under negative pressure, and the second ink tank is under positive pressure.

3. The ink delivery system as described in claim 1, wherein, The negative ink line is connected to the first ink port, the positive ink line is connected to the second ink port, and one or more inkjet printheads are interconnected between the positive ink line and the negative ink line.

4. The ink delivery system as described in claim 3, wherein, Each inkjet printhead is contained within a printing module with localized pressure control.

5. The ink delivery system of claim 1, further comprising the bulk ink supply source connected to the first ink tank via an ink supply line.

6. The ink delivery system of claim 5, further comprising a filling pump positioned in the ink supply line.

7. The ink delivery system as described in claim 6, wherein, The first ink can has a first ink height sensor, and the filling pump is controlled to pump ink from the bulk ink supply source to the first ink can in response to the first ink height sensor sensing a predetermined ink height in the first ink can.

8. The ink delivery system as described in claim 7, wherein, The second ink tank has a second ink height sensor, and the ink pump is controlled to pump ink from the first ink tank to the second ink tank in response to the second ink height sensor sensing a predetermined ink height in the second ink tank.

9. The ink delivery system of claim 1, wherein the ink delivery system is configured to circulate ink from the second ink tank through one or more inkjet printheads and to return the ink to the first ink tank.

10. A method for controlling a first ink pressure and a second ink pressure in respective first and second ink tanks during printing, the first ink tank and the second ink tank having respective first and second air lines connected to a main air line, the method comprising the steps of: - An air pump operably connected to the main air line between the first air line and the second air line; - The first ink pressure and the second ink pressure are controlled using a first airflow restrictor and a second airflow restrictor located in the main air line; and - Print from one or more inkjet printheads in: - Relative to the airflow direction through the main air duct, the first airflow limiter is upstream of the first air duct, and the second airflow limiter is downstream of the second air duct; and - The first ink tank and the second ink tank are connected in a fluid circuit containing the inkjet printhead.

11. The method of claim 10, wherein, The first airflow limiter and the second airflow limiter are adjustable.

12. The method of claim 10, wherein, The first airflow limiter and the second airflow limiter can be controlled independently.

13. The method of claim 10, further comprising the step of locally controlling the ink pressure in each inkjet printhead during printing.

14. The method of claim 10, further comprising the step of replenishing the ink in the second ink tank by pumping ink from the first ink tank to the second ink tank.

15. The method of claim 14, further comprising the step of replenishing the ink in the first ink tank by pumping ink from a bulk ink supply source to the first ink tank.

16. The method of claim 10, wherein, The first ink tank is under negative pressure, and the second ink tank is under positive pressure.

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