Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-17
2001-10-02
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S054000
Reexamination Certificate
active
06296348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus which records an image on a recording sheet by causing recording particles to jump and then directly depositing the particles on the recording sheet such as a paper sheet.
2. Description of the Related Art
A recording apparatus is disclosed in U.S. Pat. No. 5,477,250. The recording apparatus has a rotatable cylindrical toner carrier which holds charged toner particles on the outer peripheral surface thereof, and a back electrode which is disposed with a gap from the toner carrier. The back electrode is electrically connected to a power source to form an electric field which electrostatically attracts the charged toner particles on the toner carrier toward the back electrode. An insulating plate having a plurality of apertures through which toner particles can pass is placed between the toner carrier and the back electrode. The insulating plate has annular electrodes which surround the apertures, respectively.
In the recording apparatus, when a voltage corresponding to an image data is applied to one of the electrodes, the toner particles in a position on the toner carrier where is opposed to the electrode are peeled off to jump into the corresponding aperture. The toner particles which have passed through the aperture are deposited on a recording sheet to form a dot. An image corresponding to the image data is recorded on the recording sheet by a mass of such dots.
In the recording apparatus, a cluster of toner particles which jump from the toner carrier is dispersed during a period when the toner particles pass through the aperture, and hence a dot formed on the recording sheet has an obscure outline and a low density. As a result, there arises the problem in that a formed image lacks sharpness. In order to solve the problem, a method has been proposed in which a converging electrode is disposed in the periphery of the aperture in the insulating plate and on the side of the back electrode with respect to the annular electrode, a constant voltage of the same polarity as that of the charged toner particles is applied to the converging electrode, and a cluster of toner particles which pass through the aperture is inwardly converged in a radial direction by an electric repulsive force, whereby a dense dot having a sharp outline is formed on the recording sheet.
However, a recording apparatus provided with such a converging electrode has the other problem in that the jumping toner particles are accelerated by an electric field formed between the converging electrode and the back electrode, and the toner particles are scattered by an impact at the collision with the recording sheet, whereby the image quality is deteriorated.
SUMMARY OF THE INVENTION
In order to solve the other problem, the direct recording apparatus of the present invention comprises:
a carrier which holds charged recording particles;
a back electrode which is opposed to the carrier to electrostatically attract the recording particles;
a PC board which is placed between the carrier and the back electrode so as to form a passage through which an image carrier passes between the back electrode and the PC board, the PC board being made of an insulating material and having a plurality of apertures through which the recording particles can pass;
a first electrode which is placed around each of the apertures in the PC board, and which, when the first voltage is applied, more strongly attracts the recording particles held on the carrier toward the back electrode and causes them to jump into the aperture;
a second electrode which is placed around each of the aperture in the PC board and on the side of the back electrode with respect to the first electrode, and which, when the second voltage is applied, converges a cluster of the recording particles passing through the aperture by an electric repulsive force, or changes a jumping direction of a cluster of the recording particles passing through the aperture; and
a control section which, in correspondence with turning off of the first voltage applied to the first electrode, controls a potential difference between the second electrode and the back electrode to become smaller.
It is to be noted that the term “in correspondence with” means not only the case where the operations are completely synchronized with each other, but also the case where they are slightly shifted in timing from each other.
In the direct recording apparatus of the present invention, in correspondence with turning off of the first voltage applied to the first electrode, a potential of the second electrode may be shifted toward a polarity which is opposite to a charge polarity of the recording particles. Alternatively, in correspondence with turning off of the first voltage applied to the first electrode, a potential of the back electrode may be shifted toward the same polarity as a charge polarity of the recording particles, or, in correspondence with turning off of the first voltage applied to the first electrode, a potential of the second electrode may be shifted toward a polarity which is opposite to a charge polarity of the recording particles and a potential of the back electrode may be shifted toward the same polarity as the charge polarity of the recording particles.
The other direct recording apparatus of the present invention comprises:
a carrier which holds charged recording particles;
a back electrode which is opposed to the carrier to electrostatically attract the recording particles;
a PC board which is placed between the carrier and the back electrode so as to form a passage through which an image carrier passes between the back electrode and the PC board, the PC board being made of an insulating material and having a plurality of apertures through which the recording particles can pass;
a first electrode which is placed around each of the apertures in the PC board, and which, when the first voltage is applied, more strongly attracts the recording particles held on the carrier toward the back electrode and causes them to jump into the aperture; and
a control section which, in correspondence with turning off of the first voltage applied to the first electrode, controls a potential of the back electrode to be shifted toward the same polarity as a charge polarity of the recording particles.
According to the direct recording apparatus of the present invention, in correspondence with turning off of the first voltage applied to the first electrode, the control section controls the potential difference between the second electrode and the back electrode so as to become smaller, and hence the electric field formed between the PC board and the back electrode is weakened. When toner particles which have jumped from the carrier and passed through the aperture of the PC board enter the weakened electric field, therefore, the acceleration is suppressed and the speed of the toner particles becomes lower than that in the related art, so that the impact at the collision with the image carrier is reduced. As a result, the toner particles are prevented from scattering on the image carrier, and it is therefore possible to record a sharp and high quality image.
In the other direct recording apparatus of the present invention, similarly, in correspondence with turning off of the first voltage applied to the first electrode, the control section controls the potential of the back electrode so as to be shifted toward the same potential as the charge polarity of the recording particles, and hence the electric field which electrostatically attracts toner particles jumping from the carrier is weakened. Therefore, the acceleration of the jumping toner particles is suppressed and the speed of the toner particles is lower than that in the related art, so that the impact at the collision with the image carrier is reduced. As a result, the toner particles are prevented from scattering on the image carrier, and it is therefore possible to record a sharp and high quality image.
REFERENCES:
patent: 5477250 (1995-12-01), Lars
Array Printers AB
Morrison & Foerster / LLP
Nguyen Thinh
Welker Matthew T.
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