JP2001121714A - Ink jet printer, ink cartridge and method of supplying ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide efficient flow of ink to a passage from an ink cartridge to an ink jet pen in a sucking device utilizing a capillary action without using a high cost and complicated sucking or vacuuming device. SOLUTION: This ink jet printer comprises an ink supplying station having a first porous member 62 with a first capillary action, a print head attached to a pen body, an ink jet pen 18 having a second porous member 66 with a second capillary action which is greater than the first one and a carriage 16 which is scanned back and forth across a printing region and intermittently positions the pen 18 to couple it with the supplying station. When the pen 18 has been coupled to the supplying station, the second and first porous members 66, 62 are coupled with fluid with each other so that the second porous member 66 receives the ink from the first porous member 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an ink storage device and a method for distributing ink to an ink jet printing device.

[0002]

2. Description of the Related Art Ink jet printers operate by ejecting droplets of ink from a printhead onto a print medium. The printhead is mounted on an ink-jet pen, which is held in the printer at an appropriate position relative to the media. When the pen is not operating, the ink must be applied to the printhead at an appropriate "back pressure" (i.e., below ambient pressure) to keep the ink from dripping from the printhead. An elastic elastomer bladder, porous foam,
A variety of mechanisms are used, such as internal accumulators, foam generators, and spring-loaded flexible bags.

US Pat. No. 4,771,295 (Baker et al.), Assigned to the assignee of the present invention, discloses the use of polyurethane foam in a print cartridge for containing ink. The use of capillary materials, such as polyurethane foam, for back pressure control offers certain advantages over other back pressure mechanisms. For example, capillary elements eliminate many of the problems arising from changes in ambient pressure and temperature. In addition, there is no need to keep the capillary material sealed to maintain back pressure.

The above Baker patent discloses a disposable "print cartridge" in which an ink reservoir is formed integrally with the printhead. When the ink is used up, the entire cartridge (including the print head) is discarded. With this device, the user ensures that a new printhead is obtained, each containing a new ink load. As printhead technology has improved, it has become possible to make the printhead a permanent or semi-permanent part of a printer.
The ink is in an ink reservoir that is replaced when empty. In some inkjet printing devices, a replaceable ink reservoir is directly connected to the pen. In other devices, the ink reservoir is located remotely from the pen and is fluidly connected to the pen by a flexible tube.

[0005] In yet another approach, the printhead includes a small on-board ink reservoir that can hold only a small amount of ink. The printhead intermittently reciprocates to an automatic refill station where it contacts a larger ink reservoir to receive a fresh ink load. The printhead then resumes printing until another ink load is needed. This device is sometimes referred to as an "intermittent refill" device or "suction" device. The present invention
It is intended for such a suction device.

[0006]

SUMMARY OF THE INVENTION U.S. Pat. No. 4,967,207 (Rude) assigned to the assignee of the present invention.
r) and 4,968,998 (Allen)
Both disclose wicking devices that use polyurethane foam in the wicking configuration. A problem with the use of polyurethane foam is that polyurethane foam cannot be sufficiently wetted by ordinary inkjet inks. Therefore, the polyurethane foam resists the flow of ink through the pores and is less likely to be refilled. In a wicking device, it is desirable that the refilling process take place as quickly as possible. To eliminate the problem of slow refilling of the foam, these two patents disclose a pressure and vacuum device that draws ink into the foam while simultaneously drawing a vacuum above the foam. But,
The problem with these arrangements is that they are complex and expensive. In the current market, inkjet
It is very important to minimize the complexity and cost of the printer.

[0007] Accordingly, there is a need for a wicking printing device that avoids the need for expensive pressure and vacuum equipment to refill the pen, and that allows a back pressure device based on capillary action. .

[0008]

SUMMARY OF THE INVENTION The present invention provides an inkjet printing apparatus that includes a printer chassis having a print area and an ink supply station mounted on the chassis. The ink supply station includes an ink reservoir in which a first porous material is installed, and the first porous material has a first predetermined capillary action. The ink is in a porous material. The printing device also includes a pen body and an inkjet printhead mounted to the pen body. Second
Is disposed on the pen body, and the porous material has a second predetermined capillary action that is greater than the first predetermined capillary action. The second porous material transfers the ink to the printhead in fluid communication with the printhead. A carriage assembly is mounted to the chassis and is configured to receive an ink jet pen and scan the pen back and forth across the print area. The carriage assembly intermittently positions the pen to contact the ink supply station. The ink supply station and the pen are configured such that when the pen is connected to the ink supply station, the second porous material is in fluid connection with the first porous material and the second porous material receives ink from the first porous material. It is configured as follows.

The present invention also provides an ink cartridge for an ink supply station of a wicking printing device. The ink cartridge includes an ink reservoir configured to be received in an ink supply station. The first porous material is located in the ink reservoir and has a first predetermined capillary action when ink is present.
The ink reservoir is intermittently connected to an ink jet pen containing a second porous material having a second predetermined capillary action and fluidly couples the first porous material to the second porous material. It is configured as follows. The first porous material is a second porous material.
Has a first predetermined capillary action smaller than the predetermined capillary action.

[0010] The present invention also relates to an ink-jet printer.
A method for supplying a print head is provided. The method includes: (a) providing a porous material to an ink cartridge; (b) providing a second porous material to an ink-jet pen; (c) filling the first porous material with ink; A) intermittently connecting the ink cartridge with the ink-jet pen; and (e) fluidly coupling the first porous material to the second porous material during the intermittent connecting step. Wherein the first porous material and the second porous material each have a critical surface tension for wetting of at least 80% of the surface tension of the ink; and (f) removing the ink from the first porous material. Flowing into the second porous material. In a preferred embodiment, the step of flowing the ink occurs by capillary action, wherein the first porous material has a first predetermined capillary action that is less than a second predetermined capillary action of the second porous material. ing.

Accordingly, the present invention provides an efficient flow of ink from an ink cartridge to an ink jet pen in a capillary action based wicking device without resorting to expensive or complex wicking or vacuum devices.

[0012]

FIG. 1 shows a printing apparatus 1 according to the present invention.
0, the controller 14, the pen carriage 16 (receiving the pens 18, 20, 22, 24), the ink tank 2
6, 28, 30, 32, a medium advance motor 36, and a chassis 1 on which a carriage drive motor 38 is mounted.
2 is provided. The chassis 12 has a paper tray 40.
Is installed. The controller 14 is communicatively connected to a host printing device (not shown), such as a personal computer, and receives therefrom data signals representing images and / or text strings to be printed. Controller 1
4 is also communicatively connected to printheads 18, 20, 22, 24, media advance motor 36, and carriage advance motor 38. The media advance motor 36 is connected by a transmission assembly 42 to a polymer roller (not shown) that drives the print media through the printer. The carriage advance motor 38 is connected to the carriage 16 via a drive belt 44. Carriage 16
Is the bar 4 when scanning back and forth across the print area.
I'm on 6. The belt 44 is an idler pulley 48
Is an endless loop held by One sheet 50 is shown in the input tray 40.

At an appropriate time, the controller 14 activates the carriage advance motor 38 to drive the carriage 16 in the carriage advance axis direction to cause the print heads 18, 20, 2 to move.
2 and 24 are scanned over the current swath of sheet 50 of print media. As the pens 18, 20, 22, 24 are scanned across the sheet or page 50, the printhead is guided by the controller 14 to form the required dot matrix pattern of ink droplets across the sheet 50. discharge. After the scan is complete, controller 14 sends a signal to media advance motor 38 to advance sheet 50 incrementally so that the printhead can begin another pass. A number of adjacent horizontal passes are printed in this way, completing the printing of the required image on the page. The space between the ink reservoirs 26, 28, 30, 32 and the idler pulley 48 can be considered a print area.

After a certain amount of printing, the pens 18, 20,
The ink contained in the nozzles 22 and 24 is consumed and needs to be refilled. When the pen is in the refill position, the ink is sent from the reservoirs 26, 28, 30, 32 into the pen, so that the pen is refilled and ready for printing. When any one of the ink tanks is depleted of ink, it is replaced with a new ink tank. At some point, the printhead itself may deteriorate. In this case, it can also be replaced by the user or a skilled technician.

FIG. 2 shows the ink reservoir 26 engaged with the pen 18, as occurs during the refill process. As previously described, the pen 18 is held inside the carriage 16 and the carriage 16 rides on a carriage bar 46.
The ink tank 26 includes a housing 60 and an internal porous member 62.
It has. The pen 18 includes a housing 64, an internal porous member 66, a print head 68, and a nozzle member 70. As shown, the pen 18 is divided into two main chambers, an accumulator chamber 72 and a plenum 74. The two main chambers are separated by a filter 76 formed from a mesh of stainless steel wire. The third porous member 78 is provided between the porous member 62 and the porous member 66. Porous member 78 is formed as part of porous member 66 and may be made of the same porous material or may be formed of a separate material. Unless otherwise indicated, this specification refers to the porous member 66,
A porous member 78 is included.

When it is time to refill the pen, the carriage motor 38 drives the carriage 16 to position the pen below the ink tanks 26, 28, 30, 32. These reservoirs are driven down by a mechanized assembly (not shown) to engage the pen 18 and bring the pen 18 into the position shown in FIG. The mechanized assembly can operate on its own motor or on one of the other motors, such as motor 36 or motor 38. Alternatively, a ramp device or sled device can be provided to lift the pen up and engage the ink reservoir when the pen is driven to a position below the ink reservoir. An annular seal ridge 80 is formed on the bottom surface of the ink reservoir 26. The elastomer gasket 82
It is placed on top of pen 18 and is configured to contact bump 80. The interface between the ridge 80 and the gasket 82 creates a vapor diffusion barrier between the ink reservoir 26 and the pen 18. The main purpose of this seal is to prevent excess evaporation of the ink while the device is not in use. However, the more the ink is displaced, the more air passages are formed in this seal to allow the air in the porous member 66 to escape.

[0017] The refilling of the pen is preferably done so quickly that the pen can resume printing as quickly as possible. This is especially true if the printing operation has to be interrupted due to the refill procedure. Therefore, it is advantageous to select the porous materials 62 and 66 that can be easily refilled efficiently. U.S. Patent No. 4,967,207 (Rude) assigned to the assignee of the present invention.
r) and 4,968,998 (Allen)
Discloses the use of polyurethane foam as a back pressure mechanism for a wicking ink-jet pen. Polyurethane foams provide good "static" back pressure due to the capillary action created by the small pores formed in the foam. However, polyurethane foam resists the flow of liquid into the foam and therefore does not have good refillability. In these patents, due to the inherently slow refilling of polyurethane foam, the ink is simultaneously siphoned into the foam, the foam is evacuated, and within a reasonable amount of time given by the constraints of the wicking device, It is necessary to use a suction / vacuum device for refilling the foam into the foam. However, the use of expensive and complex wicking mechanisms is disadvantageous in the current inkjet market.

The ability of a capillary element to provide capillary pressure results from the interaction of three physical components: liquid, solid, and gas. For present purposes, the liquid is an inkjet ink, the solid is a capillary material, and the gas is air. Capillary pressure depends on the surface tension of the liquid, the bonds between the liquid molecules and the adhesion between the solid and liquid molecules forming the capillary element. An important method of measuring the molecular interaction between a liquid and a solid that forms a capillary element is the contact angle θ that occurs when the liquid is placed on the solid. To measure this contact angle, a drop of the selected liquid is placed on a flat piece of the selected solid. If the drop beaded on the solid, make an angle measurement between the liquid and the solid. This angle is the contact angle.
When air is present, each liquid and solid pair has a particular contact angle θ. If the liquid spreads completely on the solid without forming a ball, the contact angle is zero.

In the proposed wicking device, the mechanism for holding ink in the stationary ink reservoir is referred to as a storage container, and the small on-board ink container in the scanning ink jet pen is referred to as an accumulator. When selecting the material for the reservoir and accumulator, it is desirable to take into account not only the stationary working capillary head, but also the dynamic resistance to ink flow. In general, highly wettable materials desirably have reduced resistance to liquid flow. Very wettable materials, ie, those with very small contact angles, have reduced flow resistance in two ways. First, it allows for a large void size, and often allows for greater penetration for a given capillary head. The measure of the ability of a capillary member, such as a capillary tube or porous material, to pull liquid upwards from a given level against gravity is called its "capillary head." In general, a capillary head can be described by the following equation:

[Equation 1] Where L _p = wet perimeter of void containing meniscus A _p = wet area of void occupied by meniscus σ = surface tension of liquid ρ = density of liquid θ = contact angle of liquid on capillary material g = gravity Constant

A small ratio of L _p / A _p corresponds to a large void size and often correlates to a large permeability.
Non-wetting materials (where the cosθ term is smaller) can achieve a higher ratio of L _p / A _p and a correspondingly smaller void size and more wettable material to achieve the same capillary head. Must have low penetration. Small void sizes and low permeability can result in unacceptable pressure drops and inadequate ink flow at high ink flow rates.

A second method by which highly wettable materials can reduce the resistance to ink flow is by reducing the threshold pressure required to initiate movement of the porous material at the meniscus of the ink. It is noted that the meniscus of a porous medium tends to exhibit hysteresis that resists movement of the air / liquid interface until a threshold pressure is reached. This phenomenon can be observed with raindrops on the windshield. The magnitude of this resistance increases as the contact angle increases. In other words, for a given liquid (eg, ink), the resistance to meniscus movement is
It is higher for a porous medium that is difficult to wet.

"Critical surface tension to wetting" is an effective concept in guiding the selection of a porous media material for this application. The critical surface tension for wetting is a speculative property of a solid. Liquids having a surface tension below this value will wet the solid easily (ie, contact angle close to 0), and liquids having a surface tension above this value will not wet the solid easily and have a high contact angle Will be. Conceptually, this can be represented by Table 1 below.

[0024]

[Table 1]

The term σ _Cr indicates the critical surface tension for wetting a solid material. As noted above, very wettable porous materials are desirable for this application. For very wet materials, the θ is as close to 0 as possible and the cos
It is possible to define θ as close to 1 as possible. In FIG. 1, this corresponds to a porous material whose critical surface tension σ _{Cr for} wetting is greater than the surface tension of the ink. The surface tension of inks marketed by the assignee of the present invention is in the range of 30 to 40 dynes / cm.
Therefore, the material selected for the storage container and accumulator should have a critical surface tension for wetting of about 40 dynes / cm or greater.

In the illustrated embodiment, a porous medium composed of bonded biaxial nylon 6 fibers is used.
The material used in this embodiment has a bulk density between about 0.13 and about 0.19 grams per cubic centimeter. The porosity is between about 80% and about 85% void volume. Nylon 6 has a critical surface tension for wetting of about 42 dynes / cm and can be easily wetted by ordinary inkjet inks. In contrast, reticulated polyurethane foam (as used in many prior art disposable print cartridges)
It has a critical surface tension for wetting of about 23 dynes / cm and is therefore inferior in the choice to minimize resistance to flow. Other materials having a high critical surface tension for wetting include glass, polyester, polyethylene terephthalate (PET), polyvinylidene chloride (PVDC) and polyvinylidene fluoride (PVDF). These materials may be commonly available in the form of a reticulated foam,
Or sometimes you can't. In addition to foams, alternative porous media foams include fibers, individual beads or particles, and sintered particles.

The porous member 62 can be formed from the same material as the porous member 66, as long as the relative capillary action is such as to ensure a positive flow from the porous member 62 to the porous member 66. To ensure this positive flow, the capillary head of the porous member 66 applied to the fluid head of the ink above the porous member 66 (both of which assists inflow into the porous member 66) Must be greater than the capillary pressure plus the pressure loss due to flow or hysteresis in the meniscus, all of which resist the inflow of ink into the porous member 66. As the porous member 66 empties, the fluid head of the ink approaches zero, and for highly wettable and highly permeable materials, the dynamic flow loss and hysteresis effects approach zero. Ink tank 2 that tends to push ink down into porous member 66
Due to the ink fluid head in 6, it is possible to construct an actuator in which the capillary pressure of the porous member 62 and the porous member 66 is the same. However, in this embodiment with the same capillary action, the refilling process is slowed and the extraction of ink from the ink reservoir is less efficient than if downstream capillary action is high. In a preferred case, the porous member 6
When the capillary pressure at 6 is greater than the capillary pressure at the porous member 62, a positive flow is ensured. Porous member 62 and porous member 6
If 6 were formed from the same material, their relative capillary pressure would be controlled by controlling their relative void size.

Advantageously, the porous material has a critical surface tension for wetting of at least 80% of the surface tension of the ink. More preferably, the porous material has a critical surface tension for wetting of at least 90% of the surface tension of the ink. In a most preferred embodiment, the porous material has a critical surface tension for wetting that is greater than or at least equal to the surface tension of the ink used. The surface tension of normal inkjet ink is
With a maximum of about 40 dynes / cm, the critical surface tension for wetting of these capillary elements is preferably at least about 32 dynes / cm, and more preferably about 36 dynes / cm.
cm. In a most preferred embodiment, the critical surface tension for wetting is at least about 40 dynes / cm, where the material is completely wetted by the ink.

It is also desirable that each successive downstream capillary material has a higher capillary pressure than the previous capillary member so that the ink is continuously drawn downstream toward the printhead. In the example device of FIG.
Must have a higher capillary action than that of the porous member 62. Each successive capillary member has at least 5.08 centimeters of water (2
It is preferred to have a tall capillary head.
In the illustrated device, porous member 62 may comprise a 2.5 inch capillary head and porous member 66 may comprise a 5 inch capillary head. Can be prepared. The printhead can generate approximately 8 inches of water to draw ink from the porous member 66.

The plenum 74 is a relatively large open chamber rather than a capillary channel. Filter 76 remains wet due to ink in plenum 74 and / or ink in porous member 66. When wet, each opening between the yarns of the mesh filter 76 impedes the passage of air. These openings are
It has a specific "bubble pressure" that does not allow the foam to pass unless the foam pressure is exceeded. Since the device typically does not exceed this bubble pressure, the filter 76 acts like a check valve, allowing air to pass in either direction. This non-return valve characteristic is that, for example, when the ink reservoir is not connected to the pen,
The plenum 74 is sealed from ambient pressure. If the plenum is not sealed, air will be drawn in and back pressure will be lost.

[0031]

The device described above is an improvement of the suction device. Acceptable and efficient refilling takes place between the storage container and the pen without the need for expensive and complicated wicking and vacuum equipment. Also, refilling occurs without the need to monitor the fluid level in the pen. Capillary device
Automatically prevent overfill condition.

[Brief description of the drawings]

FIG. 1 is a perspective view of a printing apparatus according to the present invention, in which a portion of a printer is indicated by imaginary lines.

FIG. 2 is a side sectional view of the ink storage container and pen assembly of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Printer apparatus 12 Printer chassis 14 Controller 16 Carriage 18, 20, 22, 24 Ink-jet pen 26, 28, 30, 32 Ink tank 62, 66 Porous member

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jeffrey Kay Pugh 97034, Oregon, United States, Lake Oswego, Maryle Creek Drive 17754 (72) Inventor, Bruce Coger 97330, Oregon, United States, Helms Drive 37194 F term (reference) 2C056 EA24 KB25 KB37 KC12 KC25 KD08

Claims (15)

[Claims] 1. A printer chassis having a print area, attached to the chassis, an ink reservoir, a first porous material installed in the ink reservoir, having a first predetermined capillary action, and An ink supply station comprising ink contained in a material, a pen body, an ink jet printhead mounted on the pen body, and mounted on the pen body and greater than the first predetermined capillary action. An ink-jet pen having a second predetermined capillary action and having a second porous material in fluid communication with the printhead for communicating ink to the printhead; and Configured to receive a pen, scanning the pen back and forth across the print area, and applying the ink to the ink supply A carriage assembly configured to be intermittently positioned so as to be connected to the ink station. The ink supply station and the pen are configured such that when the pen is connected to the ink supply station, An ink jet printing apparatus, wherein the second porous material is fluidly coupled with the first porous material such that the second porous material receives ink from the first porous material. . 2. The ink jet printing apparatus according to claim 1, wherein the second porous material has a critical surface tension for wetting of at least 80% of the surface tension of the ink. 3. The inkjet printing apparatus of claim 1, wherein the second porous material has a critical surface tension for wetting of at least 90% of the surface tension of the ink. 4. The method according to claim 1, wherein the first porous material and the second porous material each have a critical surface tension for wetting equal to or greater than the surface tension of the ink. The inkjet printing apparatus according to claim 1. 5. The method according to claim 1, wherein the second predetermined capillary action is the first capillary action.
The ink jet printing apparatus of claim 1, wherein the predetermined capillary action is at least 5.08 centimeters (2 inches) greater than the water column. 6. An ink cartridge for use in an ink supply station of a suction printing apparatus, comprising: an ink tank configured to be received by the ink supply station;
A first porous material having a predetermined capillary action, wherein the ink reservoir is intermittently provided with an ink-jet pen having a second predetermined porous material having a predetermined capillary action. And the first porous material is configured to fluidly couple the first porous material with the second porous material, wherein the first porous material is less than the second predetermined capillary action. An ink cartridge having a predetermined capillary action. 7. The ink cartridge of claim 6, wherein the first porous material has a critical surface tension for wetting of at least 80% of the surface tension of the ink. 8. The ink cartridge of claim 6, wherein the first porous material has a critical surface tension for wetting of at least 90% of the surface tension of the ink. 9. The ink of claim 6, wherein the first porous material has a critical surface tension for wetting equal to or greater than the surface tension of the ink.
An ink cartridge according to claim 1. 10. The method of claim 6, wherein the first predetermined capillary action is at least 5.08 centimeters (2 inches) greater than the second predetermined capillary action.
An ink cartridge according to claim 1. 11. A method of supplying ink to an ink jet printhead, comprising: providing a porous material to an ink cartridge; providing a second porous material to an ink jet pen; filling the first porous material with ink. Intermittently connecting the ink cartridge with the ink-jet pen; fluidly coupling the first porous material to the second porous material during the intermittently connecting step; Wherein the first porous material and the second porous material each have a critical surface tension for wetting of at least 80% of the surface tension of the ink; and Flowing from the porous material to the second porous material. Supply method. 12. The method according to claim 11, wherein the first porous material and the second porous material each have a critical surface tension for wetting of at least 90% of the surface tension of the ink. The described method. 13. The method of claim 12, wherein the first porous material has a critical surface tension for wetting equal to or greater than the surface tension of the ink. 14. The step of flowing the ink is performed by capillary action, wherein the first porous material has a first predetermined capillary action smaller than a second predetermined capillary action of the second porous material. The method of claim 11, comprising: 15. The method of claim 1, wherein the second predetermined capillary action is at least 5.08 centimeters (2 inches) greater than the first predetermined capillary action.
4. The method according to 4.