Patent Application
20090179928
This patent specification claims priority from Japanese Patent Application No. 2008-006258, filed on Jan. 15, 2008 in the Japan Patent Office, the entire contents of which is hereby incorporated by reference herein.
1. Field of the Invention
The present invention relates to an image-forming apparatus, and more particularly, to an image-forming apparatus that is equipped with a recording head for ejecting ink droplets and a transport belt for transporting sheets of recording media onto which the ink droplets are ejected to form an image.
2. Discussion of the Background
As an image-forming apparatus, such as a printer, a facsimile machine, a plotter, or a multifunction machine including at least two of these functions, a liquid-ejecting image-forming apparatus such as an inkjet recording device that uses a recording head for ejecting ink droplets is known.
There are two types of the liquid-ejecting image-forming apparatuses. A serial-type image-forming apparatus forms images using a recording head that ejects ink droplets while moving in a main scanning direction. By contrast, a line-type image-forming apparatus forms images using a recording head that remains stationary while ejecting ink droplets.
In either case, the liquid-ejecting image-forming apparatus forms images by ejecting the ink droplets from the recording head onto a sheet of recording media while the sheet is being transported. Therefore, the transport characteristics of the image-forming apparatus profoundly affect imaging performance.
Such a liquid-ejecting image-forming apparatus is equipped with a maintenance-recovery mechanism that performs maintenance and recovery, in other words cleaning, of a recording head for ejecting the ink droplets.
The maintenance-recovery mechanism for the recording head generally includes a moisturizing cap, a suction cap, wiper members, wiper cleaners, and an idle ejection receiver.
The moisturizing cap seals a nozzle surface of the recording head so as to keep the nozzle surface moist and prevent it from drying out.
The suction cap is connected to a suction mechanism, such as a suction pump, that suctions and discharges ink the viscosity of which has increased from the nozzle. It is to be noted that the moisturizing cap may serve as the suction cap as well.
The wiping members (wiper, wiper blade) wipe and remove any ink adhering to the nozzle surface. The wiper cleaner cleans the wiper. The idle ejection receiver receives the ink droplets that are ejected in an idle ejection that is a clearing operation and do not contribute to forming images.
Such cleaning is performed in various ways. Thus, for example, in one known liquid-ejecting image-forming apparatus, a head unit containing the recording head pivots to an upright position, after which the head unit slides to a position facing a maintenance-recovery unit so as to be cleaned.
In another known liquid-ejecting image-forming apparatus, even during printing, in order to cap a head unit that is not in use, a maintenance-recovery unit is disposed downstream from the head unit in a direction in which a recording media is transported.
Additionally, a known liquid-ejecting image-forming apparatus includes a transport unit to transport sheets using a transport belt, an image-recording unit such as a recording head that is equipped with several ink-ejecting ports aligned in the same direction as a direction in which the transport unit transports the sheets, and a release mechanism that switches the transport unit between an image-recording state and a release state to facilitate removal of a jammed sheet.
In the image-recording state, the transport unit can transport the sheets close to the ink ejecting ports. In the release state, the transport unit is disengaged from all ink releasing ports and is almost parallel to or inclined with respect to the image-recording unit.
As a separate matter, it is to be noted that when a liquid-ejecting image-forming apparatus forms images, a gap between a reading head and a surface of the sheet must be kept constant, that is, maintained at a predetermined or given distance. Therefore, a distance between the recording head and a surface of the transport belt is generally adjusted according to a thickness of a sheet of recording media used in an image forming operation.
Thus, in another known liquid-ejecting image-forming apparatus, the head unit is mounted on a sliding device that includes a vertically moving mechanism, and a surface position of a recording media is detected so that the gap is adjusted to a predetermined or given distance.
As an additional complication, in the above-described image-forming apparatus, line-type recording head units are widely used in order to improve a printing speed. A known line-type recording head unit includes nozzle lines each of which extends in an entire width of the sheet. In another known line-type recording head unit, each nozzle line is formed by multiple recording heads arranged to extend in an entire width of the sheet.
In order to maintain and recover such line-type recording heads, generally, configurations like those described below are adopted.
In one configuration, both multiple line-type recording heads and maintenance-recovery mechanisms (maintenance mechanisms or cleaning mechanisms) are arranged in alternating rows in a direction in which the sheet is transported, and the line-type recording heads and maintenance-recovery mechanisms move repeatedly relative to each other in both horizontally and vertically to carry out the cleaning of the recording heads.
However, such a configuration is relatively complicated. Moreover, in the above-described configuration, the distance between the multiple line type recording heads is longer, and accordingly, color deviation, which means that the different color ink droplets are not properly aligned in a multicolor image on the sheet, is likely to occur.
In another configuration, the maintenance-recovery mechanism is located in the shoulder of sheet transport route, which is out of the sheet transport route in a direction orthogonal to the sheet transport route, and the line type recording head rotates to the maintenance-recover mechanism.
However, in this configuration, a depth of the image-forming apparatus is relatively long.
In view of the foregoing, one illustrative embodiment of the present invention provides an image-forming apparatus that includes a head unit configured to include line type recording heads for ejecting ink droplets, a transport mechanism disposed facing the recording head and configured to transport a sheet, a maintain-recovery mechanism disposed downstream from the transport mechanism in a direction in which the sheet is transported and configured to maintain and recover the line type recording heads, and a head moving mechanism configured to move the head unit, between a position facing the transport mechanism and a position facing the maintain-recovery mechanism, in the direction in which the sheet is transported.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve a similar result.
It is to be noted that, in the present application, “image-forming apparatus” means the device that ejects the ink to a recording media, such as paper, thread, fiber, textile, metal, plastic, glass, ceramic, etc., so as to form images thereon, and “image forming” includes both forming on the recording media an image including a pattern, etc., that has no commonly understood meaning as well as image including a letter and/or an illustration that does have a given meaning. Further, “ink” is not limited to only the materials generally called “ink” but also used as a generic term for the liquid, such as recording-liquid, fixing liquid, other liquid, etc., that can form images.
Moreover, “transfer sheet” includes not only paper but also any materials to which ink can adhere, such as an overhead projector (OHP) sheet, textile, etc., and is used as a generic term for all types of recording medium, recording paper, a recording sheet, etc.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and particularly to
Referring to
The head unit 1 includes line type recording heads 11 (11k, 11c, 11m, and 11y) that eject ink droplets. The ink supply device 2 supplies the ink to the recording heads 11 in the head unit 1. The transport unit 3 is disposed facing the recording heads 11 in the head unit 1 and transports a sheet P. The sheet feeder 4 feeds the sheet P to the transport unit 3.
The maintenance-recovery unit 5 maintains and recovers, that is, cleans, the line type recording heads 11 in the head unit 1. The sheet P is discharged onto the discharge tray 6. The head drive unit 7 moves the head unit 1 between a position facing the transport unit 3 and a position facing the maintenance-recovery unit 5 in a direction indicated by arrow A shown in
Referring to
The multiple recording heads 11y, 11m, 11c, and 11k eject yellow, magenta, cyan, and black liquid ink, respectively, and include multiple heads 11a, shown in
It is to be noted that the subscripts Y, M, C, and K attached to each reference numeral indicate only that components indicated thereby are used for forming yellow, magenta, cyan, and black images, respectively, and hereinafter may be omitted when color discrimination is not necessary.
Referring to
It is to be noted that, because the sub-tanks 21 are located at a position lower than that of the recording heads 11 in the head unit 1 so as to balance the force of the ink dripping down from the recording heads 11 and the force of the ink returning to the sub-tanks 21 through the ink supply tubes 24, a required negative pressure is generated in the recording heads 11.
The head unit 1 is held in a base member assembly 12 that consists of a first base member 12A and a second base member 12B. The first base member 12A holds the head unit 1, and the second base member 12B holds the first base member 12A movably at least in a vertical direction. Further, the sub-tanks 21 of the ink supply unit 2 and the branching portions 22 are mounted on the second base member 12B.
Further, the second base member 12B is connected to a timing belt 73 that is wound around a driving roller 72 and a driven roller 74 of the head drive unit 7.
As the driving roller 72 rotates, driven by a driving motor 75, the driven roller 74 is rotated, and thus the timing belt 73 is rotated. Therefore, the second base member 12B moves in the sheet transport direction.
Thus, the head unit 1 moves between the position facing the transport unit 3 and the position facing the maintenance-recovery unit 5 in the sheet transport direction indicated by arrow A shown in
In this way, because the head unit 1 and the sub-tank 21 of the ink supply unit 2 are held on the base member assembly 12, and more specifically, the second base member 12B, and are moved together therewith, the image-forming apparatus can prevent changes in the pressure in the supply tubes 23 and 24, which connect the sub-tanks 21 to the recording heads 11, caused by deformation of the supply tubes 23 and 24 as the head unit 1 and the sub-tank 21 of the ink supply unit 2 move together with the second base member 12B of the base member assembly 12. The ability to maintain a constant pressure in the supply tubes 23 and 24 is important to maintaining consistent imaging quality.
It is to be noted that, alternatively, when the image-forming apparatus adopts a method of directly supplying ink from the ink cartridges to the recording heads instead of via the above-described sub-tank ink supply method, the ink cartridge itself can be mounted directly on the second base member 12B.
Referring to
The transport belt 31 disposed facing the head unit 1 transports the sheet P that is fed by a separation roller 41 and a feed roller 42 one by one. The transport belt 31 is an endless belt wound around the transport-driving roller 32 and the transport driven roller 33. As the transport-driving roller 32 rotates, driven by a belt driving motor, not shown, the driven roller 33 is rotated, and thus the transport belt 31 is rotated.
Multiple suction holes, not shown, for attracting the sheet P to the transport belt 31 by sucking air therethrough are formed on a surface of the transport belt 31 so that the transport belt 31 can transport the sheet P.
The suction fan 34 sucks air through the suction holes on the transport belt 31 to create a vacuum that attracts the sheet P to the transport belt 31 and holds it there.
It is to be noted that attraction of the sheet P is not limited to air suction creating a vacuum, and alternatively, the sheet can be attracted to the transport belt 61 using other methods such as electrostatic attraction, adhesion, etc.
The gap control unit 35 controls a gap between a nozzle surface of each recording head 11 in the head unit 1 and the surface of the transport belt 31, that is, the sheet transport surface.
The transport unit 3 can pivot on the driven roller 33 in a direction indicated by arrow B shown in
The home position, which herein is also called a first position, is close to the recording units 11, and is indicated by solid lines shown in
The release position, which herein is also called a second position, is removed from the recording units 11, and is indicated by broken lines shown in
Thus, the transport belt 31, the suction fan 34, the gap control unit 35 etc., are pivotable as a single integrated assembly between these two positions.
When the transport unit 3 is at the home position, the sheet P can be transported, and the head unit 1 can perform printing.
On the other hand, when the transport unit 3 is at the release position, a sheet that is jammed in the transport unit 3 can be removed. That is, because a downstream portion of the transport unit 3 in the sheet transport direction pivotally moves down when the transport unit 3 moves to the release position, removing the jammed sheet is relatively easy. Further, the head unit 1 can prevent or reduce interference between the nozzle surface of the recording head 11 in the head unit 1 and the transport belt 3 when the head unit 1 slides to the side of the maintenance-recovery unit 5.
Referring to
The release mechanism driving motor 81 and the pinion 82 are fixed on a base of the image-forming apparatus, in other words, an apparatus frame, and the sector gear 83 is fixed on a unit frame, not shown, of the transport unit 3.
As the pinion 82 rotates, the sector gear 83 rotates, thereby enabling the transport unit 3 to pivot and change position.
It is to be noted that, although a timing belt, gears, etc., are used to transmit the rotation of the release mechanism driving motor 81 to the pinion 82, for simplicity those components are omitted from the drawings.
The maintenance-recovery unit 5 is equipped with a cap member 51 that caps the nozzle surfaces of the recording heads 11. Above the maintain-recovery unit 5, a transport guide member 9 that covers the maintenance-recovery unit 5 is disposed. The transport guide member 9 can be rotated in a direction indicated by arrow C shown in
When the transport guide member 9 is at an open position indicated by broken lines shown in
When the transport guide member 9 is at a closed position indicated by solid lines shown in
The sheet feeder 6 is equipped with an end fence 62 and a side fence, not shown.
Maintenance and recovery, that is, cleaning, of the recording heads 11 is described below with reference to
First, as the transport unit 3 pivots to the release position in a direction indicated by arrow B1, the transport guide member 9 is rotated and opened in a direction indicated by arrow C1 so as to expose the top of the maintenance-recovery unit 5.
Subsequently, the driving motor 75 (shown in
After the cap member 51 caps the nozzle surfaces of the recording heads 11, a vacuum unit, not shown, cleans the recording heads 11 by sucking the ink therein from the nozzles through the cap member 51.
After the nozzle suction as the maintenance and recovery of the recording heads 11 is completed, the head unit 1 returns to the former position facing the transport unit 3 (printing position), and the transport guide member 9 is closed. Thereafter, the image-forming apparatus can perform printing.
As described above, the maintenance-recovery unit that maintains and recovers the line type recording heads is located downstream from the transport unit in the sheet transport direction, and the head unit is moved reciprocally in the sheet transport direction between the position facing the transport unit and the position facing the maintain-recovery unit.
As a result, cleaning of the head unit 1 can be performed by a relatively simple mechanism, minimizing depth of the image-forming apparatus.
Further, the recording heads can be arranged in parallel in the sheet transport direction at relatively short intervals, and therefore the distance between the respective colors decreases and thus reduces color deviation, which means that the different color ink droplets are not properly aligned in a multicolor image on the sheet. Thus, image quality can be improved.
Referring to
The gap adjustment unit 35 includes an eccentric cam 37 attached to a rotary shaft 36 that is rotated by a driving motor, not shown. A rotational angular position of the eccentric cam 37 is detected by an encoder, not shown.
It is to be noted that, alternatively, the rotation angle can be controlled by a stepping motor.
Initially, referring to
Thus, a gap between the transport unit 3 and the nozzle surfaces of the recording heads 11 in the head unit 1 is set to a height that depends on a rotation position of the eccentric cam 37 in the gap adjustment unit 35.
By contrast, referring to
Therefore, after the head unit 1 is cleaned, after which the head unit 1 is slid back to the position facing to the transport unit 3 as described above, by pivoting the transport unit 3 back to the home position, shown in
Referring to
It is to be noted that, (a), (b), and (c) in
Next, another embodiment of the present invention is described below, with reference to a plan view shown in
Next, another embodiment of the present invention is describes, with reference to a schematic perspective side view illustrating an overall configuration shown in
In the embodiment shown in
When the transport unit 30 pivots from the home position to the release position, respectively shown in
It is to be noted that the head unit 1 is urged by a spring, not shown, in a direction indicated by arrow E shown in FIG. 10. When the positioning pin 39 engages the positioning hole 15, as shown in
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-006258 | Jan 2008 | JP | national |
