Electrophotography – Image formation – Development
Reexamination Certificate
2000-11-20
2002-01-22
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Development
C399S057000, C399S058000
Reexamination Certificate
active
06341209
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for METHOD FOR CONTROLLING INK AGITATING DEVICE OF A LIQUID ELECTROPHOTOGRAPHIC COLOR PRINTER earlier filed in the Korean Industrial Property Office on Nov. 20, 1999 and there duly assigned Serial No. 51746/1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a control method of an ink agitator of a wet-type electrophotography printer, and more particularly to a control method of an ink agitator of a wet-type electrophotography printer.
2. Description of the Prior Art
Generally, a wet-type electrophotography printer forms an electrostatic latent image by shooting a laser beam onto a photosensitive medium such as a photosensitive belt, and prints the desired image by developing the electrostatic latent image with a developer liquid that is mixed from a liquid carrier having a solid toner and a solvent and having a predetermined coloring, and then copying the same image on to printing paper.
In one wet-type electrophotography printer, a belt shape photosensitive medium is wound on rollers which are installed within the printer main body, and the medium is installed such that it rotates in a fixed orbit. Around this photosensitive medium, units including an electrification unit, exposure unit, developing unit, drying unit, and copy/fixing unit are installed. In addition, near the developing unit, there is installed a developer supply device which continuously supplies developers of certain concentration to the developing unit. Here, the developer is a mixture of concentrated ink containing a powdered toner and a liquid carrier, in which the toner is at approximately 24 wt %. The toner includes pigments that represent yellow, magenta, cyan, or black colors.
The developer supply device includes numerous circulation tanks which store developers that are to be supplied to the developing unit, numerous injection nozzles which spray the developer within each circulation tank on to the development gap of the developing unit, numerous ink storage tanks which store concentrated ink that correspond to respective colors that are to be supplied to the circulation tanks, a carrier storage tank which stores the carrier that is to be supplied to the circulation tanks, a waste tank for collecting used developers that come from the circulation tanks, and a developer filling and used-developer collecting unit for recovering used-developers collected in the waste tank with a refill cartridge that is empty inside, along with refilling the concentrated ink or carrier of a refill cartridge to the ink storage tank or carrier storage tank. In addition, the developer supply device is provided with concentration measuring sensors for measuring the concentration of the developer stored in the circulation tank, and an ink agitation device for agitating the concentrated ink stored in the ink storage tank.
The ink used in the wet-type electrophotography printers is composed of a hydrocarbon solution which is an insulating dispersion media, organosol which is an organic substance serving as a binder, pigments which are dyes, and charge directors which are salts yielding positively and negatively charged ions, such that the ink may possess electrical characteristics. An example of this type of ink is disclosed in U.S. Pat. No. 5,652,282, to Baker et al., entitled LIQUID INKS USING A GEL ORGANOSOL.
A wet-type electrophotography printer which uses this type of ink to form images must regularly agitate the ink, which is the developing substance, during operation. One characteristic of this ink is that, when left alone for a substantial amount of time, a phenomenon occurs in which the organosol constituent, which is distributed throughout the developer liquid, deposits and turns into lumps, and therefore the deposited ink must be dispersed again.
The concentrated ink within the ink storage tank of the developer supply device has approximately a 17% % Solid concentration, and the developer in the circulation tanks has approximately 2.3 to 3.5% % Solid concentrations. The actual requisite concentration is around 3%, but concentrated ink is used so that a larger amount of ink may be supplied using the same capacity ink storage tank. If, however, a more highly concentrated ink than that currently used is stored, the viscosity of the ink becomes too high and operations of appropriately dispersing and supplying the developer become difficult. Given the same amount of time since the ink was last agitated, an ink storage tank that contains highly concentrated developer requires more time to disperse the developer than that of the circulation tanks containing a developer of lower concentration.
Because of the above reasons, the ink agitator which is provided in the developer supply device of a printer includes agitation wings which are rotatably installed in each ink storage tank, a motor which is the driving power source for the agitation wings, and force transmission unit which conveys the driving force of the motor to the agitation wings. The force transmission unit includes follower pulleys which are mounted on the upper end of the rotation shaft of the agitation wings, a driver pulley which is mounted on the shaft of the motor, and a belt which is installed such that it winds and goes around the follower pulleys and the driver pulley.
The control method of an ink agitator composed as above will now be described. When power is turned on and the printer performs initializing operations, the ink agitator is driven and starts to agitate the ink stored in the ink storage tanks. The driving of the ink agitator stops at the completion time of initialization and the agitation operation is completed.
Then, the printer displays an indication that the printer is in the ‘READY’ state, and when there is data to be printed the printer performs printing. Here, the initialization operation period of the printer is approximately 1.5 minutes to 2 minutes. That is, the agitator is driven for 1.5 to 2 minutes and dissolves deposits and lumps of ink by agitating the ink in the ink storage tanks.
However, because the conventional ink agitator control method described above controls the agitator such that the agitator is driven only during the initialization time, for example, 1.5 to 2 minutes, for all situations including cases where the printer has not been turned on for a substantial amount of time (for example, more than seven days), there is a difficulty in maintaining an adequate concentration of the developer because ink deposits and lumps of ink have not been completely dissolved.
Furthermore, if the concentrated ink that has not been completely dispersed is supplied to the circulation tanks from the ink storage tanks, concentration in the circulation tank is detected inaccurately. Additionally, the undispersed particles accumulates in the tubular developer supply paths and eventually the paths get clogged, leading to and faulty development and preventing high quality image printing.
On the other hand, to resolve the above problems, the ink may be completely dispersed by prolonging the initialization time. However, this causes other problems related to inconvenience in printer usage due to long waiting and standby times.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved electrophotographic printer and printing method.
A further object of the invention is to provide an electrophotographic printing method which provides uniform dispersion of ink before printing.
A yet further object of the invention is to provide a printing method which shortens the waiting time for printing.
The present invention is disclosed taking into consideration the problems set forth, and provides a control method for an ink agitator of a wet-type electrophotographic printer that allows uniform dispersion of ink within liquid carriers, which is the dispersion media, through complete dissolving of deposition and lumps even f
Kim Jong-woo
Lee Hyong-gu
Bushnell , Esq. Robert E.
Grimley Arthur T.
Sasung Electronics Co., Ltd.
Tran Hoan
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