KR100532297B1 - Printing system with air accumulation control means enabling a semipermanent printhead without air purge - Google Patents

Abstract

An inkjet printing system 10 having a semi-permanent printhead 12 having a fluid inlet portion supplied with ink and an ejector portion for ejecting ink in response to a control signal is disposed. The printing system also includes a replaceable ink supply 14 configured to store ink volumes and provide ink to the printhead. This printhead can sustain the entire life of multiple ink volumes. The printing system includes a fluid accumulator portion in fluid communication with the printhead and the replaceable ink supply. Without purging the air from the printhead, the fluid accumulator will receive air entering the printhead while using the ink supply.

Description

Inkjet Printing System {PRINTING SYSTEM WITH AIR ACCUMULATION CONTROL MEANS ENABLING A SEMIPERMANENT PRINTHEAD WITHOUT AIR PURGE}

The present invention relates to inkjet printers and the like, and more particularly to inkjet printing systems using semi-permanent printheads that do not require an air purge mechanism.

Inkjet printing systems often use inkjet printheads mounted on cartridges that are moved back and forth across print media such as paper. As the printhead is moved across the printhead, the control electronics activate the ejector portion of the printhead to eject or eject ink droplets from the ejector nozzle onto the print media to form images and text. The ink supply unit supplies ink refills to the printhead ejector unit. One such fronthead is disclosed in WO 97/16315, published May 9, 1997. International Publication No. WO 97/16315 discloses a printer comprising a print cartridge for ejecting ink droplets onto a printing medium through a printhead. The print cartridge includes an ink plenum that receives ink from the ink reservoir through a plumbing conduit. The flexible bag is kept at atmospheric pressure inside the print cartridge. The flexible bag activates the regulator and accumulator inside the print cartridge. The flexible bag expands and contracts to compensate for changes in pressure and temperature that occur while the pressure regulator is shut off and affect air trapping inside the print cartridge.

Some printing systems use a replaceable ink supply separate from the printhead. When the ink supply is exhausted, the ink supply is removed and replaced with a new ink supply. When an exchangeable printhead can use multiple ink supplies, it is referred to as a "semi-permanent" printhead. This is exchanged with each ink container, in contrast to the disposable printhead.

In semi-permanent printheads, premature failure due to failure of proper pressure regulation is an important issue. To understand this damage, it is necessary to consider the operating state of the printhead. In order to operate properly, many printheads is typically narrow range of negative -1inchH ₂ O to -6inchH ₂ O (i.e., O ₂ to -25.4mmH -152.4mmH ₂ O) - work that must be maintained at a gauge pressure () Has a pressure range. Gauge pressure refers to the pressure measured in comparison to atmospheric pressure. In this specification, the pressures will all be gauge pressures. If the pressure is positive, the printhead and print system storage will be adversely affected. During printing, positive pressure can cause drops to drip or clump. During storage, ink may flow out of the printhead by positive pressure. Ink spilled during storage can be wrapped and solidified on the printhead and printer components. This agglomerated ink can permanently damage the drop ejection of the print head, resulting in costly printer maintenance. To avoid positive pressure, the printhead uses internal mechanisms to maintain negative pressure.

Air in the printhead can interfere with the maintenance of negative pressure. When the printhead is initially filled with ink, bubbles often remain. In addition, during the life of the printhead, air accumulates due to many factors such as the removal of decomposed air from the ink, called dispersion and outgassing from the external ambient atmosphere to the printhead. While the surrounding environment changes, such as a temperature increase or pressure drop, the air inside the printhead will expand in proportion to the total amount of air received. This expansion counters the internal mechanism to maintain negative pressure. Internal mechanisms within the printhead can compensate for changes in the environment within limited limits, even if the environment changes abruptly. The printhead pressure outside this range will be positive.

One solution to the air accumulation problem lies in the use of disposable printheads. The amount of ink associated with the disposable printhead can be adjusted to keep the air accumulation below the threshold. If the ink amount is small, the printing cost increases because it frequently requires replacement of the printhead. As a variant, the ink container can be enlarged to reduce the frequency of printhead changes. However, the enlarged ink container becomes a problem when the printing application is a compact desktop printer. One example of a system using a disposable printhead, wherein a large ink supply is replaced each time the printhead is replaced, is a continuous ink refill system for disposable inkjet cartridges having a predetermined ink capacity. Disposable Ink Jet Cartridges Having a Predetermined Ink Capacity, "US Patent No. 5,369,429.

Another solution to the air accumulation problem is to use an air purge mechanism that can implement a semi-permanent printhead. An example of an air purge method is disclosed in US Pat. No. 4,558,326, entitled "Purging System for Ink Jet Recording Apparatus." Problems with the purge system include (1) printer costs added by the purge mechanism, (2) reliability issues associated with the adjustment of ink to purge out with air (which can increase printer maintenance requirements), and (3) Residual air in the printhead ink ejector (if air is purged through the ink ejector). In particular, the air purge mechanism can increase the maintenance requirements of the printer.

Accordingly, there is a need for a printing system that uses a semi-permanent printhead using ink transfer technology that enables a relatively compact size desktop printer that is inexpensive, low failure and reliable.

Summary of the Invention

The present invention relates to an inkjet printing system having a semi-permanent printhead having a fluid inlet for receiving ink and an ejector portion for ejecting ink in response to a control signal. The printing system further includes a replaceable ink supply structure of a structure for supplying ink to the print head which stores a predetermined amount of ink. The print head can last for a lifetime of multiple ink volumes. The printing system includes a fluid accumulator portion in fluid communication with the printhead and the replaceable ink supply. When using the ink supply without purging the air from the printhead, the fluid accumulator receives the air introduced into the printhead.

A preferred embodiment of the present invention relates to an ink conveying apparatus fluidly coupled to a fluid inlet to provide ink to a printhead. This ink transfer device controls the air entering the printhead so that the accumulator can accommodate all the air entering during the life of the printhead.

1 is a schematic representation of a printing system according to the present invention, showing an air source affecting the printing system;

2 is a perspective view showing a preferred embodiment of a printer according to the present invention;

3 is a schematic view showing a preferred embodiment of a printhead according to the present invention;

4 is an isometric view of a preferred embodiment of a printhead according to the invention,

5A-5C are schematic cross-sectional views taken along line 5A-5A of FIG. 4,

6 is an isometric view of a printhead ready to be inserted into a carriage portion of a printing system according to the present invention;

7A is an isometric view of a printhead prepared for connection to a conduit outlet, in accordance with the present invention;

FIG. 7B is a cross sectional view showing a conduit outlet taken along line 7B-7B in FIG. 7A;

7C is a cross-sectional view showing the fluid connection between the conduit outlet and the printhead in accordance with the invention taken along line 7B-7B in FIG. 7A;

FIG. 8 is a cutaway view of an ink supply receiving station of the type used in the printing system of FIG. 2 with the ink supply ready to be inserted into the ink supply receiving station; FIG.

9A is a cross-sectional view of the fluid outlet and conduit inlet taken along line 9A-9A in FIG. 8 prior to the fluidic connection between the fluid outlet and the fluid inlet;

9B is a cross sectional view showing a fluid connection between the fluid outlet and the conduit inlet taken along line 9A-9A in FIG. 8;

10 is an exploded view in isometric view of parts according to a preferred embodiment of the ink container 10 prior to assembly of the ink container 10;

11 is an isometric view of a preferred embodiment of the ink container 10,

12 is a plot of temperature versus air solubility,

Fig. 13 is an isometric view illustrating a modified embodiment of the ink container according to the present invention, and a printhead having an ink container arranged to be in fluid connection thereto.

1 is a schematic diagram illustrating an inkjet printing system 10 according to the present invention. The printing system 10 has a printhead 12 fluidly coupled through a fluid conduit 16 to an exchangeable ink supply or container 14.

When the printhead 12 receives ink from the fluid conduit 16, the ejector portion 18 selectively ejects ink onto a medium (not shown) under the control of the printing system control electronics 20. The printhead 12 has a fluid inlet 22 fluidly connected to a conduit outlet 24 coupled with the fluid conduit 16.

The fluid conduit 16 receives ink from the replaceable ink supply 14. The fluid conduit 16 has a conduit inlet 26 fluidly coupled to a fluid outlet 28 associated with an exchangeable ink supply 14.

During printing, ink may flow from the ink supply 14 via the fluid conduit 16 to the printhead 12 so that ink droplets may be ejected by nozzles (not shown) associated with the ejector 18. Since the printhead 12 is semi-permanent, it is possible to print a large amount of ink. Thus, the ink supply portion 14 is periodically replaced. In the preferred embodiment, the printhead 12 is expected to sustain while 450 cc (cubic centimeters) of ink is being printed. In this embodiment, each ink supply 14 supplies 30 cc of ink to the printhead 12, whereby the printhead 12 is expected to sustain while 15 ink supplies are used.

One feature of the present invention relates to air accumulation limitations and the acceptance technology of air accumulated in the printing system 10. As indicated in FIG. 1 and below, printing system 10 has multiple sources of air that ultimately accumulate in printhead 12.

1) Initial Air -relates to the air bubbles that exist before the printhead 12 is installed in the printing system 10.

2) Printhead Connection -relates to the air introduced when the printhead 12 connects to the fluid conduit 16.

3) Conduit Startup -relates to the air initially present in the fluid conduit 16, which enters the printhead 12 when the printing system 10 is first used.

4) Diffusion -relates to air that diffuses into the printhead 12 and fluid conduit 16 during the life of the printhead 12.

5) Ink Supply Connections -Relate to the incoming air when each ink supply 14 is connected to the fluid conduit 16.

6) Free Air of the Ink Container— Refers to the bubbles present in the ink supply 14, which are extracted from the fluid conduit 16 and then move through the fluid flow to the printhead 12.

7) Degassing -relates to the air coming out of solution as the ink penetrates the printhead 12.

Another feature of the present invention is an accumulator mechanism in which the printhead 12 receives air entering the printing system 10 by said source. In order to prevent it from flowing out of the printhead 12, it is very important to keep the internal pressure of the printhead 12 negative. When the printhead 12 experiences ambient temperature and pressure excursions during the nonprinting period, the bubbles inside the printhead 12 will tend to expand and increase the pressure in the printhead 12. The printhead has an accumulator 29 that compensates for this expansion and maintains negative pressure. However, this accumulator 29 has an upper limit of the volume which can be corrected. This is called the "warehouse capacity" of air.

The "storage capacity" of the accumulator 29 depends on the design and environmental operating range of the accumulator. This environmental range is defined by the upper limit of temperature and / or the lower limit of pressure at which the accumulator 29 must withstand the maximum of bubble expansion. In a preferred embodiment, the upper limit of this temperature is 140 degrees Fahrenheit (60 degrees Celsius) at constant pressure. That is, the accumulator must allow for the expansion of the same amount of air as the storage capacity up to a temperature of 140 ° F. (60 ° C.). In an exemplary embodiment, the storage capacity is 4.5 cc (cubic centimeters). In other words, this exemplary accumulator must compensate for the expansion of 4.5 cc bubbles over ambient temperature (approximately 70 ° F. (21 ° C.)) to 140 ° F. (60 ° C.) to maintain negative pressure in the plenum.

Another feature of the invention relates to an “air budget” adopted to ensure that the air source does not exceed the storage capacity. In the air budget, you choose how much air to allocate for each air source. Exemplary air budgets are made in Table 1 below: Example air budget Air budget items by air source Air budget Early 0.3cc Printhead connection 0.1cc Conduit boots 1.3cc Diffusion (Plumbing, Printhead) 1.0cc Ink supply connection 0.1cc Free air in the ink supply section (container) 0.1cc Degassing 1.6cc

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Total air budget = 4.5 cc

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The sum of all budget items equals the storage capacity of 4.5 cc. Each and every budget item may increase, provided that other items are correspondingly reduced to ensure that the total air budget does not exceed the storage capacity of the air.

Another feature of the invention relates to the technique used to ensure that each air source is kept at a sufficiently low level so that the total accumulated air is below the storage level. These techniques for receiving air and limiting air introduction will be described below with reference to FIGS.

2 shows a diagram of one preferred embodiment of a printing system 10. The printing system 10 includes a media input tray 30A and a media output tray 30B for storing print media (not shown), respectively, before and after the print media is supplied to the print zone 32. The carriage 34 supports a plurality of printheads 12 and scans the surface of the print zone 32 so that a plurality of ejectors 18 associated with the printheads 12 can selectively inject ink onto the print media. To help. Each printhead 12 receives ink from any of a plurality of corresponding ink supplies 14 via a fluid conduit 16.

The printhead 12 is semi-permanent because they can use multiple ink containers 14. This makes the printing system 10 compact. The ink supply 14 of the preferred embodiment uses various color inks including black 14b, blue 14c, magenta 14m, and yellow 14y. The black ink container 14b has a capacity of approximately 75 cc, and the color ink containers 14c and 14m each have a capacity of approximately 30 cc. There is also a larger 75cc black ink container and a plug compatible 30cc black ink container. The size of the ink container is chosen small enough to avoid adversely affecting the size of the printing system 10 and to take into account shelf life. They are chosen large enough to adequately lower the exchange rate. Since each printhead 12 can withstand approximately 450 cc of ink usage, each printhead must utilize multiple ink containers 14 and therefore must be semi-permanent.

The storage capacity of the printhead 12 will be described with reference to FIGS. 3, 4, and 5A-5C. 3 is a schematic diagram illustrating a printhead 12 connected to a fluid conduit 16. The printhead 12 receives ink at the inlet pressure from the fluid conduit 16 and then transfers the ink to the ejector 18 at a controlled internal pressure lower than the inlet pressure. Ejector 18 is fluidly coupled to plenum 38 that stores a quantity of ink at a controlled internal pressure. The ink passes through the filter element 39 before reaching the ejector 18 to remove particulate matter. The negative pressure in the plenum 38 is controlled using a regulator comprising an actuator 40 and a valve 42. As the ejector 18 ejects ink onto the print media, the ink in the plenum 38 is consumed. This reduces the pressure in the plenum 38. When the internal pressure reaches the low pressure threshold, the actuator 40 correspondingly opens the valve 42 so that ink passes from the fluid conduit 16 to the plenum 38. This inflow raises the pressure of the plenum 38. When the internal pressure reaches the high pressure threshold, the actuator 40 responds by closing the valve 42. That is, the pressure in the plenum 38 is regulated between the low pressure threshold and the high pressure threshold.

4 shows an isometric view of a preferred embodiment of the printhead 12. The printhead 12 includes a fluid inlet 22 to receive ink from the fluid conduit 16 and an ejector portion 18 to selectively eject ink onto a print medium (not shown). The printhead 12 further includes an internal regulator to be described with reference to FIGS. 3 and 5A-5C. The internal regulator has an air conduit 43 which will be described with reference to FIGS. 5A-5C.

5A-5C are schematic cross-sectional views showing the printhead 12 taken along line 5A-5A in FIG. The internal structure of the printhead 12 is simplified to more clearly show the functional aspect of the pressure regulating system in the printhead 12. When comparing FIG. 5A to FIG. 5C with FIG. 3, like numerals are used for like elements.

The print head 12 has an outer housing 44 that supports the ejector portion 18. The plenum 38 is in fluid communication with the ejector portion 18. Inside the plenum 38 is an actuator 40 and a valve 42 for selectively supplying ink to the plenum 38.

The valve 42 includes a nozzle 46 fluidly connected with the fluid inlet 22 for introducing ink into the plenum 38, and a valve seat 48 for sealing the nozzle 46. . The valve seat 48 is formed of an elastic material to ensure a reliable sealing of the valve. The valve seat 48 is fixedly mounted to a pressure regulator lever 50 that rotates about the regulator shaft 50A. As shown in FIGS. 5A-5C, the rotation of the lever 50 opens and seals the valve 42 as the pressure changes in the plenum 38.

The printhead 12 also has an accumulator lever 52 that rotates about the accumulator shaft 52A. A spring 54 connects the regulator valve lever 50 to the accumulator lever 52 and biases the levers toward each other. The spring is connected relatively closer to the accumulator shaft 52A than the regulator shaft 50A.

An inflatable bag 56 is disposed between the accumulator lever 52 and the regulator lever 50. The first surface of the inflatable bag 56 communicates with the outside atmosphere via an air conduit 43, and the second surface of the bag 56 is in contact with the ink in the plenum 38. Thus, the bag 56 expands and contracts in response to the pressure difference between the plenum 38 and the outer atmosphere. Bag 56, regulator lever 50 and spring 54 act together as actuator 40 as described with reference to FIG. 3.

5A shows the initial state of the printhead 12 when the bag 56 is fully retracted. When printing starts, the bag 56 expands to correct the amount of ink ejected by the ejector 18. The size of the bag is increased until one side begins to press the accumulator lever 52 and the other side begins to press the regulator lever 50 while opposing the force exerted by the spring. When the pressure of the bag 56 becomes large enough, the levers start to pivot in opposite directions to the outside.

Since the moment applied to the accumulator lever 52 by the spring 54 is smaller than the moment applied to the regulator lever 50 by the spring 54, the accumulator lever 52 moves first. The accumulator lever moves until it contacts the outer housing 44, as indicated by FIG. 5B.

When the accumulator lever 52 is fully inflated, as shown in FIG. 5C, the regulator lever 50 begins to move, so that the valve seat 48 rises away from the nozzle 46 and the valve ( 42) Open. Ink then flows from the fluid conduit 16 through the nozzle 46 into the plenum 38. The incoming ink increases the pressure in the plenum 38, reducing the force of the bag 56 on the levers 50, 52 and causing the valve 42 to close. At this time, the print head 14 is in the state shown in Fig. 5B.

As mentioned above, it is important that negative pressure is maintained in the plenum 38. The accumulator functions to maintain negative pressure even when there is air in the plenum 38. Because of the relative attachment point of the spring 54, the accumulator lever is in a pressed state against the housing 44 during normal operation. Due to printhead life, bubbles 58 tend to accumulate in printhead 12. During the storage and idle periods of the printing system 10, the ambient temperature may change. According to the ideal gas law, the bubble 58 expands in response to the temperature rise, which causes the bag 56 to contract. As the bag 56 shrinks, the accumulator lever 52 moves to maintain the pressure applied to the bag 56. Accumulator lever 52 and bag 56 thereby ensure a constant negative pressure in printhead 12 and prevent positive pressure throughout the range of motion of accumulator 52.

In an exemplary system, the range of motion of the accumulator lever 52 is up to 4.5 cc accumulated in the plenum 38 while maintaining negative pressure in the plenum 38 over a specific environmental operating range. Allows air storage capacity. If the accumulated air exceeds 4.5 cc, the printhead 12 may leak, causing damage to the printhead and the printer and affecting the operation of the ejector 18. Therefore, the cumulative amount of all air sources must be maintained below the storage volume of 4.5 cc.

There are other ways to provide pressure regulators and accumulators. Referring to FIG. 3, the valve 42 may be an electromechanical valve such as a solenoid valve. Actuator 40 may be a pressure transducer that provides a signal to the circuit for opening and closing valve 42. In order to provide the capacity for accumulating air, the outer wall of the plenum 38 must be at least partially flexible. One way to do this is to provide a rubber diaphragm 60 that separates the plenum 38 from the outside atmosphere. The rubber diaphragm 60 can move as the bubble expands, acting as the accumulator 29. As a variant, the plenum 38 may be surrounded by a spring loaded bag that similarly functions as the accumulator 29. Each variant accumulator device will have its own air accumulation limit and thus storage capacity. In order to prevent the adverse effects of positive pressure, the sum of the air sources must be kept below this storage capacity.

The air sources and techniques used to keep them within their respective budget ranges will now be described with reference to FIGS. 6 to 13. It is an important feature of the present invention to account for and control each air source in the budget to meet the overall budget target.

The first air source is the initial air in the printhead 12 before the printhead is installed in the printing system 10. In an exemplary embodiment, 0.3 cc of air is budgeted for the air source, which diffuses into the printhead 12 between the air introduced by the manufacturing process, the manufacture and installation of the printhead 12. Air to be extracted and air extracted from the printhead 12 through the fluid inlet 22 or the ejector unit 18 are included. To minimize these values, many design and assembly methods are used to fabricate the printhead 12, as described below.

When the printhead 12 is manufactured, air enters as the printhead 12 is filled with ink. In order to minimize this air, the following ink filling process is used. (1) First, by providing a source of CO ₂ gas to the fluid inlet 22 and a vacuum source to the ejector 18 of the print head 12, almost all of the gas remaining inside the print head is converted into CO ₂ gas. The printhead 12 is flushed with CO ₂ gas until done. (2) Next, the printhead 12 is degassed by providing a degassing ink source to the fluid inlet 22 and a vacuum source to the ejector 18 until the printhead 12 is filled with ink. Ink with dissociated oxygen below the saturation level). Any bubbles remaining behind during the filling process will consist mainly of CO ₂ and will quickly dissolve in the ink. Also, because the ink is degassed, all impurities (air, etc.) in the bubbles will be absorbed by the ink.

Also, in order to minimize the diffusion of air into the printhead 12 between the ink filling process and the process of installing the printhead 12 in the printer, the printhead 12 is made of a highly air diffusion barrier material. In a preferred embodiment, the outer housing 44 of the printhead 12 is made of LCP (liquid crystal polymer). In addition, other highly blocking materials such as PET (polyethylene terephthalate) or metallized plastics will work effectively. The bag 56 is preferably formed of a multilayer plastic film, at least one layer having a high air diffusion barrier property. Preferred high barrier material is polyvinylidene chloride (PVDC).

As shown in FIGS. 6 and 7, a second air source is introduced when a “printhead connection” is made between the conduit outlet 24 and the fluid inlet 22. 6 shows the initial installation of the printhead 12 into the carriage 34. The print head 12 is installed in the carriage 34 by being generally inserted downward. Upon insertion, the conduit outlet 24 is connected to a fluid inlet 22 coupled to the printhead 12.

Details of the fluidic connection between the fluid inlet 22 and the conduit outlet 24 are further described with reference to FIGS. 7A-7C. FIG. 7A shows the printhead 12 prepared for fluid connection to the conduit outlet 24. 7B shows the conduit outlet 24 before fluidic connection. 7C shows the completed fluid connection between the fluid inlet 22 and the conduit outlet 24.

The fluid inlet 22 associated with the printhead 12 includes a hollow needle 62 extending downwardly with a closed and blunt end, a blind bore (not shown), and a transverse hole 66. do. The blind bore is fluidly connected to the nozzle 46 shown in FIGS. 5A-5C. The needle is surrounded by a shroud 68.

Conduit outlet 24 includes a hollow cylindrical housing 70 extending upwards. The hollow housing 70 has an inlet 72 in fluid communication with the fluid conduit 16. The hollow housing 70 has an upper end supporting a precut bulkhead 74 that is secured to the housing 70 by a crimp cap 76. The sealing member 78 is pressed against the partition 74 by the spring 80.

When the printhead 12 is installed in the carriage 34, the shroud 68 facilitates aligning the partition 74 with the needle 62. The upper end of the conduit inlet 24 is sized to properly engage the fluid inlet 22. The top diameter of the conduit inlet 24 should be small enough to be accommodated in the shroud 68, but to ensure a reliable fluid connection between the needle 62 and the partition 74, the fluid inlet 22 It must be large enough to control the change in alignment between and the conduit outlet 24. During fluidic connection, the needle 62 penetrates the partition 74 to place the sealing member 78 downward in the cylindrical housing 70. Thus, in the final position inserted, ink will flow from the fluid conduit 16 into the housing inlet 72 and into the transverse holes 66, blind bores and nozzles 46 around the sealing member 78. May be (FIGS. 7A-7C).

To maintain within the air budget, it is important that a minimum amount of air enter the printhead 12 during fluid separation and recombination between the conduit outlet 24 and the fluid inlet 22. Once the printhead 12 is separated from the fluid conduit 16, there may be a negative pressure in the fluid conduit 16 which creates a tendency to suck air into the conduit outlet 24. To prevent this, the partition wall 74 is self-sealed immediately after the needle 62 is pulled out, preventing air from entering the fluid conduit 16. However, with a longer service life, the partition wall 74 is in a compressed state and does not immediately self seal when detached from the needle 62. To ensure immediate and reliable sealing, sealing member 78 provides extra sealing to conduit outlet 24. The air budget in Table 1 allocates 0.1 cc of air for this fluid desorption and recombination, but the entity inlet air is a negligible amount for the printhead 12 because of the reliable self-sealing properties of the conduit outlet 24.

The third air source is the air in the fluid conduit 16 when the printhead 12 is initially installed and is referred to as "piping start" air. In an exemplary embodiment, this provides less than 1.3 cc of air to the printhead 12. Referring back to FIG. 1, the fluid conduit 16 may not be initially filled (empty) to address reliability issues. For example, during transportation from the place of manufacture to the consumer, the printing system 10 may experience sudden temperature changes that cause freezing and swelling of the ink in the fluid conduit 16 that will damage the fluid conduit 16. For this reason, the fluid conduit 16 is initially shipped from the factory in a dry state.

The fourth source of air is the diffusion of air from the outside into the fluid conduit 16 and the printhead 12, which occurs during the printhead 12 installation in the printing system 10. In an exemplary embodiment, the total diffusion amount is maintained at 1.0 cc or less by using a highly air diffusion barrier material to make printheads and conduits. As mentioned above, the printhead is made of a highly diffusion barrier polymer. Fluid conduits include plumbing fixtures made from materials with low air diffusivity with an oxygen permeability coefficient of 100 cc · mil / (100 in ² · day · atm) at 23 ° C. (0 ° C.) relative humidity. do. Examples of flexible polymers suitable for this piping system include PVDC (polyvinyl chloride copolymer), ECTFE (ethylenechlorotrifluoroethylene) and PCTFE (polychlorotrifluoroethylene) copolymers.

As shown in FIGS. 8, 9A and 9B, the fifth air source is an ink supply connection between the ink supply 14 and the fluid conduit 16. 8 shows the ink supply 14 ready to be inserted into the receiving station 36 in a downward direction, in which details that do not belong to the present invention have been removed. The ink supply 14 has a fluid reservoir 82 in fluid communication with the fluid outlet 28. When the ink supply 14 is removably inserted into the receiving station, the fluid outlet 28 engages with the conduit inlet 26 to allow ink to flow from the fluid reservoir 82 to the fluid conduit 16 and to the printhead. To (12) (FIG. 1).

The ink supply connection is further described with reference to FIGS. 9A and 9B, which are cut cross-sectional views that include only fluidic connections, taken along lines 9A-9A in FIG. 8. 9A shows fluid outlet 28 and conduit inlet 26 prior to fluid connection.

The fluid outlet 28 associated with the ink supply 14 has a hollow cylindrical boss 84 extending downward from the ink supply chassis 86. The hollow boss 84 has an upper end in fluid communication with the reservoir 82, and a lower end supporting the pre-slit partition wall 88 fixed to the boss 84 by the crimp cap 90. The sealing member 92 is pressed against the partition 88 by the spring 94.

Conduit inlet 26 includes an upwardly extending hollow needle 96 having a closed, blunt top, blind bore (not shown), and transverse hole 98. The blind bore is fluidly connected to the transverse bore 98. An end of the needle 96 opposite the lateral hole 98 is fluidly connected to a fluid conduit 16 that provides ink to the printhead 12. The sliding collar 100 surrounds the needle 96 and includes a flexible portion 102. The sliding collar 100 is biased upward by the spring 104 to keep the flexible portion 102 in a position to seal the lateral hole 98 from the outside atmosphere.

Conduit inlet 26 further includes an upwardly extending boss 105 surrounding the sliding collar 100. The upwardly extending boss 105 provides protection for the needle 96, support for the sliding collar 100, and alignment for the fluid outlet 28.

9B shows the fluid connection between the fluid outlet 28 and the conduit inlet 26. When the ink supply 14 is installed in the receiving station 36, the lower end or the distal end of the fluid outlet 28 first engages with the tapered portion 105a and the inner surface 105b of the boss 105, and the needle ( 96). The lower end of the fluid outlet 28 then presses the sliding collar 100 downward. At the same time, the needle 96 enters the partition 88 and passes through the partition 88 to arrange the sealing member 92 above the cylindrical boss 84. Thus, in the fully inserted position, ink flows from the ink supply reservoir 82 through the boss 84 and around the sealing member 92, along the transverse hole 98, fluid conduit 16 and printhead 12. Can be introduced into.

Removing the ink supply 14 causes the partition 88 to escape from the hollow needle 96 and return the fluid outlet 28 and the conduit inlet 26 to the state shown in FIG. 9A.

Fluid outlet 28 is sized to reliably engage fluid inlet 26 to prevent air ingress into fluid conduit 16. The fluid outlet 28 has a length sufficient to properly engage the sliding collar 100 and to press the sliding collar 100 far enough from the lip 105c, which is a transverse bore 98 ) And the hollow boss 84 inside. The lower end of the fluid outlet 28 has a diameter small enough to be accommodated in the boss 105, but the needle 96 and the partition wall when joining the tapered portion 105a and the inner surface 105b of the boss 105. 88) should be large enough to control the change in alignment between them.

Because a number of ink supplies are connected and disconnected to the conduit inlet 26, a minimum amount of air is applied to the fluid conduit 16 during fluid separation and reconnection between the conduit inlet 26 and the fluid outlet 28. Is very important. Once the ink supply 14 is separated from the fluid conduit 16, there may be some negative pressure in the fluid conduit 16 which creates a tendency to suck air into the conduit inlet 26. To prevent this, when the ink supply 14 is separated, the sliding collar immediately seals the lateral hole 98. On the fluid outflow side, the partition wall 88 and the sealing member 92 immediately self seal, preventing air from being sucked into the ink supply portion 14. This is important to prevent air inflow when the ink container 14 is removed and reinstalled. The air budget in Table 1 allocates only 0.1 cc of air as the air for the ink supply 14 connection for the printhead 12 life.

The sixth air source is "free air of the ink supply (container)" or bubble in the ink supply 14 which is sucked from the ink supply 14 to the printhead 12 through the fluid conduit 16. This free air is initially present in reservoir 82 and / or fluid outlet 28. In a preferred embodiment, the ink supply 14 is installed in a generally vertical orientation as shown in FIG. All free air will tend to rise by flotation to the top of the ink supply 14. Because of this arrangement, the allocation value of "free air of the ink supply part" in the air budget is 0.1 cc.

However, if sufficient free air is present in the ink supply 14, when the ink in the ink supply 14 is almost running out, free air may be transferred to the fluid conduit 16. Therefore, it is desirable to limit the total volume of bubbles that can accumulate in the ink container 14.

Free air in the ink supply is mainly influenced by the material and manufacturing process of the ink supply. 10 and 11 show exploded and assembled views of a preferred embodiment of the ink supply unit 14, and details not belonging to the present invention are not shown. Referring to Fig. 10, the assembly of the ink assembly 14 includes the following steps.

1. providing a chassis 86 comprising an outwardly extending fluid outlet boss 84 and a peripheral sealing surface 106;

2. Attaching and sealing the film sheet 108 to the peripheral sealing surface 106 to form the reservoir 82, wherein the film sheet has a high air dispersion barrier multilayer structure, which in a preferred embodiment The layers comprising nylon, metallized (silver) PET and LDPE,

3. assembling the spring 94, the sealing member 92, the pre-slit bulkhead 88 and the crimp cap 90 to the boss 84 to form a fluid outlet 28;

4. injected into the opening (110) to charge the CO ₂ and an ink supply by the vacuum exhaust through the filling inlet port 110, comprising the steps of washing with CO _2, the CO ₂ injection and vacuum exhaust process, remaining in the reservoir (82) Repeating until there is substantially no air,

5. After evacuating through the filling opening (110), filling the ink supply unit with degassing ink through the filling opening (110),

6. sealing the filling port 110 immediately;

7. Sealing the elastically assembled ink supply 14 with the cap 112 and the shell 114, as shown in FIG.

The foregoing process mainly minimizes initial and accumulated free air in two ways. First, as described for the printhead 12, the CO ₂ cleaning and degassing ink filling process effectively removes the initial free air in the ink supply 14. Second, the material selected for the film sheet 108 minimizes the diffusion of air into the fluid reservoir 82 to maintain accumulated air below the threshold at which air begins to be transferred to the fluid conduit 16.

The seventh air source of air accumulation in the printhead 12 is degassing. This degassing mechanism is a change in solubility that occurs when ink passes through the plenum 38 of the printhead 12. Ink is introduced into the plenum 38 to cause air to diffuse from the ink into the bubbles in the plenum 38 when the solubility of the air dissolved in the ink is reduced. This solubility decrease is mainly driven by temperature, as described above.

FIG. 12 shows solubility curves for water showing water solubility of water temperature air. As can be seen from the curve, the water solubility decreases as the temperature rises. The thermal inkjet inks associated with the present invention are at least partially aqueous. Therefore, there are many that have air solubility curves in a shape similar to that shown in FIG.

When the printhead 12 is operating, the ejector portion 18 warms the ink in the plenum 38. This causes the ink near the ejector portion 18 to supersaturate with air such that air diffuses from the ink into the bubbles in the plenum 38. As a result, the bubbles increase in size.

One way to reduce the amount of degassing is to include anti-outgassing additives that have the effect of reducing the slope of the solubility curve. Preferred additives having this effect are ethoxylated glycerol. However, additional anti-degassing additives suitable for use in the present invention include 2-pyrrolidone, N-methyl pyrrolidone, ethylene glycol, 2-propanol, 1-propanol, cyclohexanol, EHPD. Include.

The following list shows more additives:

(a) Ketones or ketoalcohols such as acetone, methyl ethyl ketone and diacetone ether.

(b) ethers such as dioxane.

(c) ethers such as ethyl acetate, ethyl lactate, ethyl carbonate and propylene carbonate.

(d) diols such as 1,4 butanediol, 1,2 pentanediol, 1,5 pentanediol and 1,2 hexanediol.

(e) polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, neopentylglycol, polyethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, glycerol and thiodiglycol.

(f) lower alkyl mono- or di-ethers extracted from alkylene glycols such as diethylene glycol mono-methyl (or -ethyl) ether and tetraethylene glycol mono-methyl (or -ethyl) ether.

Preferably, the anti-degassing additive, which may be one or a mixture thereof, is present at least 2% by weight and more preferably 12% or more by weight. Examples of inks with adjusted degassing properties are as follows:

Composition weight%

Deodorizing Additives 12

(Esosylate glycerol, etc.)

Colorant 6

(C.I.Direct Black 52) Ink Carrier 80

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(Water + additional solvent)

Additional Components of Composition 2

(E.g., biosides, surfactants, smear control agents, buffers, etc.)

The exemplary black ink described above has an average slope of the solubility curve reduced to approximately 1/2 or less of water solubility between approximately 25 ° C. and 60 ° C. Looking at another method, the change in water solubility of the air for the ink between approximately 25 ° C. and 60 ° C. is reduced by approximately half of the change expected for water by adding the additive. As a result, preferred black inks with such additives have a degassing rate reduced to less than ½ a over the degassing rate of water. For this reason, 1.6 cc of air is the budget allocation.

A feature of the ink supply unit 14 that will increase the degassing rate is ink pressurization. Pressurization is usually performed for printing systems that require a high print rate to eliminate the pressure drop effect between the reservoir 82 and the printhead 12. Referring to Fig. 11, a preferred embodiment of the ink supply unit 14 includes pressurizing means 116 associated with the ink supply unit 14. The pressurizing means 116 may be a pump integral with the ink supply 14. As a variant, the pressurizing means 116 may be an air inlet in fluid communication with the area surrounding the reservoir 82. At this time, the pressurized gas supply source may be connected to the pressurizing means 116 to pressurize the ink supplied in the fluid reservoir 82. In both cases, the pressurizing means provides pressurized ink to the fluid outlet 28.

Pressurization will increase the gas solubility in the ink contained in the ink supply 14 according to Henry's law. When a constant pressure is applied, the ink will become more saturated with air over time, which increases the degassing rate of the ink as it moves to the printhead 12. One way of reducing insoluble air is that the pressurizing means 116 is an intermittent pressure source. The intermittent pressure source pressurizes the ink to be transferred to the fluid conduit 16 when printing is required and normally releases the pressure at the fluid outlet 28 when the printing system 10 is idle. Since most of the time is unprinted, this intermittent pressure source minimizes degassing contributed by pressurization.

Various sources of air accumulation and techniques for keeping accumulated air within budget have been described above. For example printing systems, they are summarized in Table 1. In the exemplary system, the sum of these sources is approximately 4.5 cc, beyond which a poor pressure regulation will appear, which will cause ink in the printhead 12 to leak into the printing system.

The printing system 10 has been described in which the fluid conduits 16 fluidly couple and separate the fluid inlet 22 and the fluid outlet 28. FIG. 13 shows another ink supply 14 'that can be plugged directly into the printhead 12' in an "on carriage" configuration. The ink supply 14 'includes a fluid outlet 28' directly connected to the fluid inlet 22 'coupled with the printhead 12', thus eliminating the need for a fluid conduit 16 between them. . This may rule out major air sources such as starting conduits or plumbing fixtures, diffusing the conduit or plumbing fixtures and hydrodynamic connections. This has the effect of increasing the life of the printhead and also reducing the air storage capacity.

Another variant is to provide pressure control and / or accumulator capacity to the ink supply 14 'rather than the printhead 12'. This will tend to simplify the entire fluid transfer system at the expense of precise pressure control of the printhead 12 '.

Claims (35)

An inkjet printing system of the type having a replaceable ink supply for providing ink to a printhead, comprising: Exchangeable semi-permanent inkjet printing having a fluid inlet receiving ink and an ejector section for selectively injecting ink in response to a control signal, and capable of printing through a plurality of ink portions of the plurality of replaceable ink supply units before replacement. Head, One of the plurality of replaceable ink supplies for storing one of the plurality of ink quantities, the replaceable ink supply configured to supply ink to an inkjet printhead; An accumulator portion in fluid communication with the inkjet printhead and the replaceable ink supply, the accumulator portion having a storage capacity for receiving air accumulated in a printing system, the accumulator portion being drawn from the printhead to suck ink into the printhead; In a state in which no vacuum is generated in the inkjet printhead for the purpose of removing air, and without purging air from the inkjet printhead for the purpose of correcting the air flowing into the inkjet printhead, the printhead And the accumulator portion capable of maintaining a printhead pressure range within a printable operating range through a plurality of ink quantities of the plurality of replaceable ink supplies. Inkjet printing system. The method of claim 1, The print head includes an internal plenum in fluid communication with the ejector portion, And a regulator valve receiving ink from the fluid inlet and providing to the plenum and opening and closing in response to a pressure change in the plenum to maintain the plenum in a predetermined negative pressure. Inkjet printing system. The method of claim 1, The printhead includes an inner plenum in fluid communication with the ejector portion, the accumulator portion includes a flexible member having a first surface and a second surface, the first surface in communication with an outer atmosphere, The second surface is in communication with the ink in the inner plenum and the flexible member contracts in response to bubble expansion to maintain the inner plenum at a negative internal pressure. Inkjet printing system. The method of claim 1, A fluid conduit fluidly connected with the printhead at one end and having the fluid inlet at the other end; Inkjet printing system. The method of claim 1, The semi-permanent printhead is capable of printing over the life of at least five replaceable ink supplies. Inkjet printing system. The method of claim 2, The valve includes a nozzle for introducing ink into the plenum and a valve seat for sealing the nozzle to stop the flow of ink into the plenum. Inkjet printing system. The method of claim 6, The valve seat is mounted to a lever pivotally mounted Inkjet printing system. The method of claim 2, The accumulator portion has a flexible member having a first surface and a second surface, the first surface communicating with an outer atmosphere, the second surface communicating with ink in the inner plenum, and the flexible member Retracts in response to bubble expansion to maintain the interior of the plenum at a negative internal pressure. Inkjet printing system. The method of claim 8, The plenum has a negative internal pressure that provides a biasing force on the flexible member, and the valve is opened by the biasing force when the biasing force exceeds a certain threshold. Inkjet printing system. The method of claim 4, wherein The fluid conduit comprises a portion formed of a highly air barrier material having an oxygen permeability coefficient of less than 100 cc · mil / (11in ² · day · atm) at 23 ° C., 0% Rh. Inkjet printing system. The method of claim 10, The highly air barrier material is a polymer selected from the group consisting of polyvinylidene chloride copolymers, polychlorotrifluoroethylene and ethylenechlorotrifluoroethylene. Inkjet printing system. The method of claim 4, wherein The exchangeable ink supply has a fluid outlet removably connected to the fluid inlet of the fluid conduit, wherein 0.02 cc or less of air enters when the fluid outlet is engaged and separated from the fluid inlet. Inkjet printing system. The method of claim 12, The fluid inlet has a needle with an outlet hole formed therein, the needle is surrounded by a sliding collar, and the outlet hole is fluidly coupled with the fluid outlet from a sealed position in which the sliding hole seals the outlet hole. The fluid outlet couples the needle and the sliding collar to move the sliding collar to a non-sealed position Inkjet printing system. The method of claim 13, The needle and the sliding collar are surrounded by a cylindrical boss and the fluid outlet is sized to be received within the cylindrical boss to provide proper fluid connection and alignment between the needle and the distal end of the fluid outlet. Inkjet printing system. The method of claim 1, The ink includes an additive that reduces the degassing rate of the ink below the degassing rate of water. Inkjet printing system. The method of claim 15, The additive is at a concentration of at least 2% by weight of the ink Inkjet printing system. The method of claim 16, The additive is at a concentration of at least 10% by weight of the ink Inkjet printing system. The method of claim 1, The accumulator part is integral with the print head. Inkjet printing system. The method of claim 1, The accumulator portion is integral with the replaceable ink supply portion. Inkjet printing system. The method of claim 19, The accumulator section provides precise pressure control to ensure ink transfer to the ejector section having a normal operating pressure range. Inkjet printing system. The method of claim 1, The exchangeable ink supply unit accommodates 10 to 100 cc of transferable ink Inkjet printing system. delete delete delete delete delete delete delete delete delete delete delete delete delete delete