Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
1998-08-12
2001-10-30
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
Reexamination Certificate
active
06309063
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an ink-jet printer for ejecting ink onto a sheet of paper held on a rotary drum to perform printing.
Recently, personal computers of high performance and low cost have become available, and the spread of personal computers has abruptly increased. In accordance with this trend, color printers have been also increasingly demanded. At the present stage, various types of ink-jet printers exist as color printers suitable for personal use.
Conventionally, there is a known ink-jet printer which can perform a continuous printing of 500 or more sheets, for example. This ink-jet printer has a rotary drum which rotates at a predetermined circumferential speed, and a print head for ejecting color inks onto a sheet of paper held on the peripheral surface of the rotary drum. The sheet is fed to the rotary drum from the front side of the rotary drum, and printing is performed in a state where the paper sheet is wound on the rotary drum. After printing, the paper sheet is separated from the rotary drum and discharged to the rear side of the rotary drum.
The print head includes nozzle units of, for example, yellow, cyan, magenta and black which are disposed along the peripheral surface of the rotary drum. Each of the nozzle units has ink-jet nozzles which are arranged across the paper sheet in the main scanning direction parallel to the axis of the rotary drum and which eject inks as the rotary drum rotates. Each nozzle unit is shifted in the main scanning direction at a predetermined rate, and returned to its initial position after a predetermined number of rotations for causing the nozzle unit to be moved by a distance equal to the nozzle pitch. Each nozzle unit scans the paper sheet simultaneously in the main scanning direction and the sub-scanning direction as described above, so as to eject ink onto the entire paper sheet.
When the printing speed of the above ink-jet printer is increased, positional deviation or vibration of the paper sheet may occur due to an impact produced by the sheet holding operation. Further, positional deviation of the paper sheet may also occur due to an impact produced by the sheet separating operation. In such a case, incorrect alignment is caused between print dots of color inks and this significantly deteriorates the printing quality.
In addition, the rotary drum is surrounded by a variety of process components in the ink-jet printer described above. Therefore, it is not easy to carry out jam state work of removing a jammed paper sheet and maintenance work of removing paper particles dropped from a paper sheet and attached to the rotary drum. Furthermore, the jam state work or the maintenance work cannot be started while rotation of the rotary drum continues due to inertia. If such work is done irrespective of the rotation of the rotary drum, the operator may have his or her fingers injured as a result of being caught between the drum and the process components. These problems serve as a factor of substantially reducing the printing speed.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an ink-jet printer capable of improving the printing speed without deteriorating the printing quality.
According a first aspect of the present invention, there is provided an ink-jet printer which comprises a medium feed-in mechanism for feeding a print medium; a rotary drum having a peripheral surface of a size larger than the print medium fed by the medium feed-in mechanism, for rotating at a constant speed; a medium holding section for holding the print medium on the peripheral surface of the rotary drum; a print head for printing an image by repeatedly ejecting ink onto the print medium held on the peripheral surface of the rotary drum while the rotary drum performs a predetermined number of rotations; a medium separating section for separating the print medium from the peripheral surface of the rotary drum; a medium feed-out mechanism for feeding out the print medium separated by the medium separating section; and a control section for controlling the medium feed-in mechanism, the rotary drum, the medium holding section, the print head, the medium separating section and the medium feed-out mechanism; wherein the control section includes drive means for sequentially driving the medium holding section, the print head and the medium separating section on the basis of the number of rotations of the rotary drum.
According to a second aspect of the present invention, the ink-jet printer according to the first aspect further comprises a housing which houses the medium feed-in mechanism, the rotary drum, the medium holding section, the print head, the medium separating section, the medium feed-out mechanism and the control section, and a movable table capable of being moved into and out of the housing together with components of at least the rotary drum, the medium feed-in mechanism and the medium holding section in a state where the components are mounted on the movable table.
According to a third aspect of the present invention, the medium separating section of the ink-jet printer according to the first aspect includes a separating member for separating the print medium at a position which a leading end of the print medium reaches when an operation of the print head is completed.
According to a fourth aspect of the present invention, the ink-jet printer according to the first aspect further comprises a housing which houses the medium feed-in mechanism, the rotary drum, the medium holding section, the print head, the medium separating section, the medium feed-out mechanism, and the control section; an opening mechanism for opening the housing; and a lock mechanism for locking the opening mechanism during rotation of the rotary drum.
In the ink-jet printer of the first aspect, the medium holding section, the print head and the medium separating section are driven on the basis of the number of rotations of the rotary drum. In this case, it can be constructed such that the print head is operated after the holding of the print medium by the medium holding section is completed, and the medium separating section is operated after the printing of an image by the print head is completed. In other words, an image can be printed on a print medium without being adversely affected by positional deviation and vibration of the print medium which may occur due to an impact produced by the operation of the medium holding section and by positional deviation of the print medium which may occur due to an impact produced by the operation of the medium separating section. Since correct alignment can be achieved between print dots of inks ejected for each rotation of the rotary drum, the printing quality can be prevented from being deteriorated due to incorrect alignment between the print dots of the inks.
In the ink-jet printer of the second aspect, the rotary drum, the components of the medium feed-in mechanism and the medium holding section, which are mounted on the movable table, can be pulled out of the housing together with the table, for example, upon occurrence of medium jam. Therefore, the unnecessary print medium can be removed easily.
In the ink-jet printer of the third aspect, the print medium can be separated from the rotary drum promptly after completion of printing.
In the ink-jet printer of the fourth aspect, the opening mechanism is locked by the locking mechanism during rotation of the rotary drum. Accordingly, the user can be prevented from being injured by the rotation of the rotary drum during the jam state work or the maintenance work. In other words, the jam state work or the maintenance work can be carried out safely and easily.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFE
Araki Izumi
Kamano Tadao
Kashiwagi Takashi
Morino Shigeru
Shibata Kyouichi
Barlow John
Brooke Michael S.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Toshiba Tec Kabushiki Kaisha
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