Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-02-22
2003-03-25
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S023000, C347S029000, C347S030000
Reexamination Certificate
active
06536864
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus for effecting the formation of images such as characters and figures on a recording medium such as a recording sheet being conveyed, and more particularly to an image forming apparatus in which, for example, a plurality of mechanisms such as a recording medium conveying mechanism and a recovering mechanism for an ink jet head for effecting image formation are driven by a single drive source.
2. Related Background Art
In recent years, with the spread of personal computers, word processors, facsimile apparatuses, etc. in offices, etc., various image forming apparatuses have been provided as the information output apparatuses of these apparatuses. Above all, image forming apparatuses such as ink jet printers for discharging ink to a recording medium to thereby form images such as characters and figures thereon are excellent in the dignity of image, printing speed, apparatus size, the balance of prices, etc. and are also easy to color and therefore are widely spread, and are used as image forming apparatuses in various fields.
Now, an image forming apparatus of this type such as an ink jet printer is generally provided with a recovering mechanism for removing thickened ink, dust, etc. adhering to the discharge ports of an ink jet head to thereby maintain a stable ink discharging function.
As such recovering mechanisms, there are known a capping mechanism having a cap for covering a surface in which the discharge ports of the ink jet head are disposed during non-recording to prevent the drying or evaporation of the ink, a wiping mechanism for removing the ink adhering to the surface in which the discharge ports of the ink jet head are disposed by the use of a blade or the like, a suction mechanism for sucking thickened ink, etc. from the discharge ports of the ink jet head or the vicinity thereof through the above-mentioned cap, etc. This suction mechanism brings the interior of the cap covering the surface in which the discharge ports are disposed into negative pressure by a pump to thereby discharge the ink from the discharge ports or the like.
Also, in the image forming apparatus, a mechanism for feeding and conveying recording mediums generally comprises an automatic sheet feeding mechanism containing a plurality of recording mediums such as recording sheets therein and separating and feeding them one by one therefrom, and a conveying mechanism disposed downstream thereof for conveying the recording medium in synchronism with image formation. The automatic sheet feeding mechanism is provided with a sheet feeding roller for pressure-contacting with the uppermost one of the stacked recording mediums and picking up and feeding the uppermost recording medium by the rotation thereof. A frictional member for usually producing an appropriate frictional force sheet feeding is provided in the pressure contact portion of this sheet feeding roller. Also, the conveying mechanism is provided with a conveying roller rotated by obtaining a driving force from a drive source, a driven roller cooperating with the conveying roller to nip the recording medium therebetween, and a paper path for the recording medium to pass between these rollers. In the sheet feeding and conveying mechanisms as described above, the recording medium fed by the sheet feeding roller is usually subjected to the adjustment (referred to also as the registration) of the conveyed position thereof in a nip portion comprised of the conveying roller and the driven roller, whereafter it is conveyed in synchronism, for example, with the scanning of the ink jet head, by the conveying roller and the driven roller, and image formation is effected.
The sheet feeding roller is generally formed with a dead zone portion which does not contact with the recording medium in conformity with rotation to decrease the conveying load thereof. This dead zone portion is designed to return to a rotated position opposed to a recording medium fed next when the sheet feeding roller effects rotation for sheet feeding and has finally effected one full rotation. Also, control is effected so that when the one full rotation of this sheet feeding roller is completed, the conveying roller on the downstream side may start the conveyance of the fed recording medium.
In the sheet feeding and conveying mechanisms as described above, motors are often used as drive sources for driving the sheet feeding roller and the conveying roller. In this case, there are a construction in which the sheet feeding roller and the conveying roller are driven by a motor, and a construction in which the driving of the sheet feeding roller and the conveying roller is controlled by discrete motors.
There is also known a construction in which a drive source for the pump in the above-described recovering mechanism is common to that for the conveying roller or the sheet feeding roller and the respective operations thereof are controlled, for example, by the changeover of the forward and reverse rotations of the motor. Specifically, the ordinary conveyance of the recording medium is effected by the forward rotation driving of the motor for driving the conveying roller, and the pump is operated by the driving of the motor in the reverse direction. In this case, the driving force is transmitted from the motor to the pump through a so-called one-way drive transmitting mechanism, whereby even when the driving of the motor is done in a direction in which the conveying roller is forwardly rotated, the driving force is prevented from being transmitted to the pump.
In the above-described construction, when the sheet feeding roller effects one full rotation for sheet feeding and performs the operation of the dead zone thereof returning to the initial position opposed to the uppermost recording medium (hereinafter referred to also as the resetting operation), the recording medium may sometimes be conveyed slightly excessively. At this time, the conveying roller on the downstream side is also being driven and as the result, the recording start position of the recording medium may sometimes deviate delicately.
Therefore, in the above-described construction wherein a common drive source is used for the conveying roller and the pump, i.e., the construction wherein the ordinary conveyance of the recording medium by the conveying roller is effected by only the driving of the drive source in the forward direction, and the driving thereof in the reverse direction is used for only the driving of the pump, it has heretofore been proposed regarding the fine adjustment of this recording start position to utilize a pendulum gear transmitting mechanism which is a one-way drive transmitting mechanism, and effect the minute reverse rotating operation of the conveying roller within the movement range of the pendulum of this pendulum gear transmitting mechanism (the dead zone range of transmission in which transmission is not effected), thereby effecting the adjustment of the recording start position.
However, in the case of a recording medium which is liable to slip during the feeding thereof by the sheet feeding roller depending on the relation between the conveyance distance of the recording medium by one full rotation of the sheet feeding roller and the distance of the paper path, or when the environment is a predetermined image forming environment regarding temperature, humidity, etc., it is sometimes the case that by the one full rotation of the sheet feeding roller, the recording medium does not arrive at the nip portion and the sheet feeding roller must be rotated by more than one full rotation. Even when the sheet feeding roller need thus be further rotated it has been necessary to further continue the rotation thereof in order to perform the above-described resetting operation of the dead zone portion of the sheet feeding roller.
Therefore, in the above-described adjustment of the recording start position, the reverse rotation of the conveying roller is effected more than in the case of ordinary fi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hsieh Shih-wen
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