Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-11-20
2001-05-15
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06231164
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a direct printing apparatus and also to a printing head for use in the direct printing apparatus. Further, the invention relates to a direct printing method for suitably employed in such direct printing apparatus and printing head.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,477,250 issued on Dec. 19, 1995 discloses a direct printing apparatus. The direct printing apparatus includes a rotatable cylinder or toner carrier retaining charged toner particles on its outer periphery, and a backing electrode spaced apart from the toner carrier. The backing electrode is electrically connected to a power source, thereby forming an electric field for attracting the charged toner particles on the toner carrier toward the backing electrode. Interposed between the toner carrier and the backing electrode is an insulating plate having a plurality of apertures through which the toner particles can pass. The insulating plate bears signal electrodes on one surface facing the backing electrode and base electrodes on the other surface facing the toner carrier, and each pair of signal and base electrodes surround the aperture.
In operation, if negatively charged toner particles are used, a positive voltage is charged to the backing electrode. In this instance, when a negative voltage is applied to the base electrode while a positive voltage is applied to the signal electrode, an electric field is formed from the signal electrode to the base electrode, which affords propelling of the negatively charged toner particles through the aperture onto a sheet substrate such as plain paper which is moving past between the insulating plate and the backing electrode. Then, with keeping the voltage applied to the base electrode unchanged, the voltage applied to the signal electrode is changed so that an electric field is formed from the base electrode to the signal electrode, thereby inhibiting an additional propelling of the toner particles.
As described, according to the prior art direct printing apparatus, the propelling of the toner particles is controlled by changing the voltage applied to the signal electrode and thereby reversing the direction of the electric field, in order to form an image of toner particles on the sheet substrate transported between the insulating plate and the backing electrode.
The direct printing apparatus, however, has a drawback that the toner particles tend to diverge in their propelling. Therefore, each resultant dot formed by the toner particles on the sheet substrate is relatively large in size than expected, reducing the density and clearness thereof.
SUMMARY OF THE INVENTION
The primary object of the invention is to provide a direct printing apparatus, a direct printing head, and a direct printing method capable of forming a dot having a high density and clear contour on the sheet substrate.
To this end, a direct printing apparatus of the invention comprises a bearing member for bearing charged printing particles thereon, a backing electrode opposed to the bearing member, and a power supply for generating an electric field that attracts the charged developer particles on the bearing member toward the backing electrode. The printing apparatus further comprises a printing head disposed between the bearing member and the backing electrode to form a passage with the backing electrode through which passage the sheet substrate can pass. The printing head includes an insulative sheet member having a plurality of apertures through which the printing particles can propel and plurality pairs of first and second electrodes. Each pair of the first and second electrodes surrounds the aperture. A first driver applies the first electrodes with a first signal in response to an image signal. The first signal has a voltage for energizing the printing particle on the bearing member to propel the same into associated aperture toward the backing electrode. Further, a second driver applies the second electrode with a second signal in response to the image signal. The second signal has a first voltage for attracting the printing particles on the bearing member to propel the same into associated apertures toward the backing electrode and a second voltage applied to the second electrode subsequent to the first voltage for forcing radially inwardly to converge the printing particles propelling in the aperture.
Preferably, the first and second electrodes are in the form of doughnut so that they surround the aperture. Advantageously, the second voltage applied to the second electrode has a different polarity from that of the printing particle.
According to a direct printing method for propelling charged printing particles through an aperture formed in an insulative member and thereby depositing the charged printing particles onto a substrate, first and second voltages having a polarity opposite to that of the charged printing particles are applied to first and second electrodes, respectively, mounted adjacent the aperture for energizing to propel the printing particles. Then, a third voltage which is different from the first voltage is applied to the first electrode for de-energizing the printing particles on the bearing member. Also, a fourth voltage which is different from the second voltage is applied to the second electrode for forcing radially inwardly to converge the printing particles propelling in the aperture.
Preferably, the first electrode is arranged on one side adjacent said bearing member (i.e., on an upstream side with respect to a propelling direction of the printing material) and the second electrode is arranged on the other side adjacent the backing electrode (i.e., on a downstream side with respect to the propelling direction).
Further, the second electrodes in the printing head may be electrically connected with each other.
According to the invention, by applying respective voltages to the first and second electrodes, the printing particles on the portion of the bearing member opposing the first and second electrodes are energized and propelled into the aperture. Subsequently, the voltage to be applied to the second electrode is changed so that the printing particles propelling in the aperture are forced radially, inwardly to be converged, and then deposited on the sheet substrate.
As described, the printing materials on the bearing member are energized intensely by the first and second electrodes and therefore a greater number of printing particles are propelled into the aperture, which ensures that the high density dot is formed on the sheet substrate.
In addition, the propelled printing particles are converged in the aperture by the voltage applied to the second electrode and therefore not only the dot but also the resultant image formed by dots has a clear contour and high density.
REFERENCES:
patent: 5477250 (1995-12-01), Larson
patent: 5767879 (1998-06-01), Tsukamoto et al.
patent: 6109730 (2000-08-01), Nilsson et al.
patent: 0 710 897 A1 (1996-05-01), None
patent: 0 753 412 A1 (1997-01-01), None
patent: 0 752 317 A1 (1997-01-01), None
patent: 0 769 384 A2 (1997-04-01), None
Hiraguchi Hiroshi
Shibata Yoshifumi
Shimada Hirokatsu
Uno Koji
Yamaki Toshio
Barlow John
Gordon R.
Minolta Co. , Ltd.
Morrison & Foerster / LLP
LandOfFree
Apparatus and method for direct printing using first and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for direct printing using first and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for direct printing using first and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2554844