Typewriting machines – Including adjustment for optimum printing plane
Patent
1998-08-21
2000-09-19
Hilten, John S.
Typewriting machines
Including adjustment for optimum printing plane
400 58, 400582, 400 56, B41J 1120
Patent
active
061201960
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an image forming device, and particular to such a device comprising a recording head which is scanned in a direction perpendicular to the travelling direction of a recording medium.
BACKGROUND ART
One type of such image forming devices is a device which employs an ink jet recording system. In the ink jet recording system, a nozzle filled with ink from an ink tank is provided with a heater which is heated in response to a heating pulse signal to thereby produce an air bubble, the pressure of which acts to eject an ink drop from the nozzle. In an image forming device employing the ink jet recording system, a plurality of nozzles are disposed in a line to form a recording head which is scanned to record an image.
As shown in FIG. 9, a recording head 103 (hereinafter referred to as simply a head) mounted on a carriage is scanned in a main scanning direction (X) to perform a printing on a paper sheet 15 column by column (17), so that a multitude of such columns are successively printed to achieve the printing of a band. Then, the paper sheet 15 is travelled in a sub-scanning direction (Y) to perform the printing of a second band next to the first band. This process is iterated so as to form an image constituted by the multitude of bands.
In recent years, a plurality of heads of different ink colors (e. g., cyan, magenta, yellow and black, etc.) are used together so that the different colors of ink are superimposed to form a full-color image. The full-color image requires printed positions of the respective colors (ink ejected positions) to be precise. For this purpose, usually as shown in FIG. 10, a linear scale 301 having slits 304 for every dot position formed therealong and a linear sensor 302 for optically detecting the presence/absence of the slit are used for providing the synchronization for ejecting ink drops, while counting pulse outputs (corresponding to the slits) from the linear sensor 302 for calculating a distance travelled by the head, thereby recognizing the exact positions to be printed on.
Also, the presence/absence of a paper sheet is detected with a paper sensor 303 which is mounted near the heads. As shown in FIG. 11, the paper sensor 303 is scanned on a paper sheet together with a carriage 120. When the paper sensor sequentially detects the left and right edges of the paper sheet, slit-count values are read out which are obtained by counting the output pulses from the linear sensor 302 and which correspond to the respective distances travelled from a reference position, thereby recognizing where in the horizontal direction and what size of paper sheet has been loaded. For such a paper sensor 303, usually a light-reflection type sensor is used which emits light outwardly and detects any reflected light.
In the present specification, the left and right edges of the paper sheet correspond respectively to the left and right sides when viewed from the upstream of the transfer of the paper sheet. Thus, it should be noted that the left and right are opposite to those when viewed from the front of the device.
In forming an image on a paper sheet, the print start and end positions, i.e., margins in the horizontal direction, are determined according to a current position of the paper sensor 303 and the respective heads, based on the position of the paper sheet (count values of the slits of the linear scale 301), taking into consideration a margin from the paper edge Pe and distances of the respective heads from the paper sensor. For example, in FIG. 11, suppose that "A" is a distance between the paper edge position Pe and the paper sensor 303 at the reference position and an amount of margin Z is to be obtained. Then, when the paper sensor 303 reaches a position Pk of [A+Z+X] the printing is started with the K head (black head being the first one in the printing direction). Then, when the paper sensor 303 reaches a position Pc of [A+Z+X+Y1] the printing is started with the C head (cyan head being the second one in the printing direction). Further,
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Copyer Co. Ltd.
Hilten John S.
Nolan, Jr. Charles H.
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