Patent Grant
7249824
1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid, such as ink, towards a recording medium. The present invention also relates to a recording device for recording, for example, an image onto a recording medium, such as a sheet material.
2. Description of the Related Art
A typical inkjet print head generally includes an ink container for holding ink; an exothermic element, i.e. a recording element, for discharging ink; and a duct for transferring ink to the exothermic element from the ink container.
Such a typical inkjet print head has a tendency to accumulate many air bubbles. These air bubbles are accumulated in the inkjet print head in several ways. For example, such an accumulation may be due to air entering the duct as a possible result of a change in the environment, or may be due to air bubbles remaining in the ink. Moreover, there are also cases where the air bubbles are generated due to exothermic heat or are formed in the process of fabrication of the inkjet print head. It is generally known that air bubbles inside the duct interfere with the flow of the ink being transferred to the exothermic element.
Air bubbles present on the main surface of the exothermic element can interfere with the formation of desired air bubbles, and moreover, an absorption effect generated by the undesired air bubbles reduces the pressure required for discharging the ink. This means that the ink cannot be discharged properly, thus leading to recording defects. Furthermore, if the air bubbles remain in the interior of an ink-supplying system, the ink cannot be sufficiently supplied to the exothermic element.
U.S. Pat. No. 5,812,165, for example, discloses a technique in which a groove is disposed inside a duct in order to prevent the ink supply from being interfered by air bubbles.
Furthermore, to reduce the air bubbles present in the interior of an ink-supplying system, the air bubbles, for example, may be removed by degassing the dissolved gas in the ink or may be prevented by providing a gas-liquid separation film in the ink-supplying system.
Moreover, to physically remove the air bubbles, the air bubbles, for example, may be removed by vacuuming the ink through ink discharge nozzles or by changing the components of the ink so as to allow easier defoaming of the air bubbles.
Removing the air bubbles by degassing the dissolved gas in the ink complicates the fabrication process of the inkjet print head. Moreover, according to this degassing technique, it is necessary to maintain a state where the air does not penetrate into the ink-supplying system during the actual use of the inkjet print head. This results in a complex structure of an ink cartridge. Moreover, this degassing technique is also problematic in that the air may enter through the ink discharge nozzles or through gaps between the components of the ink cartridge as time passes, meaning that maintaining the degassed state of the ink is extremely difficult.
On the other hand, providing the gas-liquid separation film requires a space in the ink-supplying system where the gas-liquid separation film is to be disposed. Moreover, an additional gas-liquid separation film must be disposed on the ink discharge nozzles in order to prevent air bubbles from entering through the nozzles.
Furthermore, removing the air bubbles by vacuuming the ink through the ink discharge nozzles is also problematic. In detail, although this technique can be effectively achieved by, for example, making the shape of a duct such that the duct is easily removable, since both the air bubbles and the ink are vacuumed at the same time, the vacuumed ink becomes a waste. Moreover, since the printer must be additionally provided with a holding component for holding the vacuumed ink and a vacuuming mechanism, the manufacture cost of the printer increases. Furthermore, depending on the structure of the vacuuming mechanism, there are cases where it is necessary to vacuum ink that contains no air bubbles. This may reduce the amount of ink that can actually be used and thus may lead to higher manufacturing costs.
According to U.S. Pat. No. 5,812,165 in which the duct is provided with a groove and has corners and edges, the capillary forces generated in the groove, the corners, and the edges may be significantly different from one another depending on how the inkjet print head is positioned during the printing process. For this reason, there are cases where the continuity of the ink-supplying path is lost.
Furthermore, if the amount of ink Q2 retained by the capillary forces of the edges and the corners become greater than the amount of ink Q1 transferred via the groove, the ink in the groove is drawn towards the corners. This may result in shortage of ink in the groove. Accordingly, the equation Q1>Q2 must constantly be satisfied. Moreover, since inkjet print heads developed in recent years move at an extremely high speed, a larger amount of ink is required per unit time, meaning that a larger amount of ink must be supplied to the inkjet print head. Accordingly, the amount of ink Q2 must also be larger.
However, retaining a larger amount of ink with the capillary forces of the edges and the corners can induce an adverse effect upon the ink-supplying path if the gas is present inside the duct. To solve this problem, more edges and corners are required. This, however, results in a complex structure of the ink container. It is therefore in great demand that a larger amount of ink be supplied stably with a simple structure.
Furthermore, depending on the tilt angle of the inkjet print head, there are cases where it is difficult to retain a sufficient amount of ink with the capillary forces generated in the edges.
The present invention is directed to a liquid discharge head and a recording device that prevent defective supply of liquid caused by air bubbles so as to achieve a stable supply of a larger amount of liquid. In one aspect of the present invention, a liquid discharge head is provided with a liquid container adapted to hold liquid; a recording element; a duct which is disposed between the liquid container and the recording element and facilitates transferring of the liquid to the recording element; and an inductive channel communicating with the duct. The inductive channel transfers the liquid from the liquid container to the recording element, and moreover, is configured to generate a capillary force greater than that of the duct. The recording element is configured to discharge the liquid transferred from the liquid container.
As described above, according to the present invention, the inductive channel communicates with the duct and transfers the liquid from the liquid container to the recording element. Since the capillary force of the inductive channel is greater than that of the duct, even if the duct is filled with gas, at least the inductive channel can stably transfer the liquid from the liquid container to the recording element.
In one embodiment, the inductive channel is configured such that an amount of liquid supplied to the recording element per unit time by the inductive channel can be greater than an amount of liquid discharged per unit time by the recording element. Accordingly, even if the duct is filled with gas, a shortage of liquid is prevented so as to allow proper discharge of the liquid. Thus, the recording process, for example, can be properly performed.
Further features and advantages of the present invention will become apparent from the following description of the exemplary embodiments (with reference to the attached drawings).
Exemplary embodiments of the present invention will now be described in detail with reference to the drawings.
Referring to
Referring to
Furthermore, a filter 6 for filtering impurities in the ink is disposed between the projection 5 and the ink absorber 2. The filter 6 not only prevents impurities from entering the duct 4 but also retains the ink drawn to the projection 5 with the meniscus force of the filter 6.
The inkjet print head further includes an ink-supplying hole 7 disposed on a side of the exothermic circuit 1 opposing the side from which ink is discharged in a direction indicated by an arrow j. The ink-supplying hole 7 continuously extends from the duct 4. The duct 4 includes a plurality of inductive channels 8a and 8b, each having a greater capillary force than the duct 4. The inductive channels 8a and 8b extend from the side surface of the projection 5 to the ink-supplying hole 7 above the exothermic circuit 1 while communicating with the duct 4. As shown in
The capillary force of each of the inductive channels 8a and 8b can be set in the following manner.
Referring to
Consequently, the ink drawn into the inductive channels 8a and 8b is transferred to the ink-supplying hole 7 by the capillary forces of the inductive channels 8a and 8b before the duct 4 is completely filled with ink. This fills up the ink-supplying hole 7, and thus forms an ink-supplying path extending continuously from the ink absorber 2 to the exothermic circuit 1. Accordingly, even if the duct 4 is filled with the gas 10, the inductive channels 8a and 8b are still capable of retaining ink.
In such a case where the duct 4 is filled with gas, in order to perform the ink supply operation only with the inductive channels 8a and 8b, the equation P1+P2+P4+P6>P5 must be satisfied. In this case, P3≈0.
The shape of the inductive channels 8a and 8b can be determined in view of the amount of ink used, the properties of the ink, the molding process, and the productivity, such that the ink can be supplied to the exothermic element only with the inductive channels 8a and 8b without underrunning the amount of ink discharged per unit time. Each of the inductive channels 8a and 8b according to this embodiment is a groove whose cross-sectional area taken along a plane perpendicular to the direction of flow is smaller than that of the duct 4. In detail, the groove is rectangular and has a cross-sectional area of about 0.5 mm×0.5 mm. Accordingly, this forms the ink-supplying path extending continuously from the ink container 3 to the ink-supplying hole 7.
With reference to
Referring to
Referring to
Subsequently, referring to
Referring to
As described above, the difference in capillary forces between the duct 4 and the inductive channels 8a and 8b allows the inductive channels 8a and 8b to be filled with ink prior to the duct 4. This achieves a state where the inductive channels 8a and 8b are constantly filled with ink in the subsequent use of ink.
Alternatively, such filling of the ink in the duct 4 may be performed by reducing the pressure inside the duct 4 when the ink is inserted to the ink absorber 2 during the fabrication of the inkjet print head. Specifically, a vacuum is first created in the interior of the inkjet print head, and the ink is then inserted to the ink container 3. Subsequently, the inkjet print head is opened, thus allowing the atmospheric pressure to force the ink to enter the duct 4.
During a recording operation by the inkjet print head having the structure described above, if gas is not present inside the duct 4, the duct 4 can smoothly transfer the ink since the flow resistance of the inductive channels 8a and 8b is greater than that of the duct 4. In this case, the ink is not substantially transferred by the inductive channels 8a and 8b.
On the other hand, if gas is present inside the duct 4, the gas causes the flow resistance of the duct 4 to be greater than that of the inductive channels 8a and 8b. In this case, the transferring of ink is mainly performed by the inductive channels 8a and 8b.
Furthermore, each of the inductive channels 8a and 8b can be a rectangular groove which is relatively unaffected by the gas inside the duct 4 even if the gas is expanded due to, for example, a change in the environment.
On the other hand, according to this embodiment, referring to
Although each of the inductive channels 8a and 8b is a rectangular groove in this embodiment, the duct 4 may alternatively be provided with a plurality of protrusions protruding towards the inner portion of the duct 4. In such a case, a capillary force is generated in a space formed between the protrusions, and such a capillary force may be used to retain the ink 11.
For example, as shown in
Thus, when the ink is retained in the inductive channels 8a and 8b or the inductive channel 8, the ink 11 can be supplied to the exothermic circuit 1 without any interference since the ink-supplying path extends continuously from the ink container 3 to the ink-supplying hole 7.
Furthermore, for further reducing the gas inside the duct 4, the inkjet print head may be turned upside down when the inkjet print head is vacuumed during the fabrication process, as shown in
Accordingly, referring to
Furthermore, referring to
According to this embodiment, the exothermic circuit 1 has four corners. Referring to
Referring to
Moreover, due to the positional difference between the inductive channels 8a and 8b, there are cases where the amount of ink and the timing of ink supplied to the exothermic circuit 1 from the inductive channels 8a and 8b may be different.
In order to uniformly supply the ink to the exothermic circuit 1 from the inductive channels 8a and 8b, the capillary forces P2a and P2b generated in the respective inductive channels 8a and 8b are set differently so that the ink can be supplied in a stable manner.
To set different capillary forces between the inductive channels 8a and 8b, the inductive channel 8a is tapered such that the width of the inductive channel 8a gradually becomes smaller in the downstream region a, as shown in
Alternatively, the inductive channels 8a and 8b may be provided with different cross-sections each taken along a plane perpendicular to the direction of flow of the ink by providing different sizes between the two, such as different widths of the grooves, different heights, and different lengths. Consequently, this allows different capillary forces between the two channels. Furthermore, in a case where the capillary force is to be generated using the protrusions 15a and 15b, two pairs of the protrusions 15a and 15b may alternatively be provided such that each of the inductive channels 8a and 8b is disposed between the protrusions 15a and 15b of the corresponding pair. In that case, the angle θ of one pair of the protrusions 15a and 15b may be set different from that of the other pair of the protrusions 15a and 15b so as to provide different capillary forces between the inductive channels 8a and 8b.
As a further alternative, the surfaces of the inductive channels 8a and 8b may be corrugated so as to give different surface structures between the two channels 8a and 8b. Consequently, this allows different capillary forces to be generated between the two channels 8a and 8b.
Furthermore, the duct 4 and the inductive channels 8a and 8b may be made of different materials, and moreover, may be formed by, for example, multi-color molding so that the materials may create different surface tensions.
Moreover, the surface of at least one of the duct 4 and the inductive channels 8a and 8b may be additionally processed in order to change, for example, the surface roughness.
Furthermore, the surface of each of the inductive channels 8a and 8b may be chemically treated for improving, for example, the hydrophilic properties so as to lower the flow resistance.
Moreover, the corners and edges of the duct 4 may be treated to provide water repellency so as to allow easier filling of ink into the inductive channels 8a and 8b.
According to such a structure, if the capillary force generated in the connecting section between the duct-forming components 3a and 3b is greater than the capillary forces of the inductive channels 8a and 8b in the duct 4, the continuity of the ink-supplying path may be lost.
In other words, referring to
Consequently, as shown in
While the present invention has been described with reference to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims priority from Japanese Patent Application No. 2003-434952 filed Dec. 26, 2003, which is hereby incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-434952 | Dec 2003 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5812165 | Boyd | Sep 1998 | A |
| 6513920 | Deshmukh et al. | Feb 2003 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20050140750 A1 | Jun 2005 | US |
