Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2001-01-23
2002-12-03
Royer, William J. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S297000
Reexamination Certificate
active
06490424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cleaning mechanism for an image forming apparatus. More particularly, the invention relates to a cleaning mechanism for an image forming apparatus for cleaning an intermediate transfer body used upon formation of an image in an electrophotographic apparatus.
2. Description of the Related Art
In an electrophotographic apparatus or the like, a toner image is electrostatically carried on a transfer member. After transfer, a substantial amount of toner resides on a surface of a photoconductor (transfer ratio is about 80 to 90%), thereby lowering image density. On the other hand, since the toner is transferred electrostatically, it is not possible to completely prevent flying toner that may degrade the clearness of the image or contaminate the inside of the apparatus. For avoiding such defects, there has been proposed a pressure type transfer means. This type of apparatus employs appropriately 200 kg/cm
2
of pressure for transferring and fixing the image. It is difficult to directly transfer the toner image on the surface of the photoconductor onto a medium to be printed and it is necessary to transfer the electrostatic latent image to a dielectric layer as an intermediate transfer body. Therefore, the apparatus can become bulky and the mechanism can be complicated. Also, when transferring the electrostatic latent image, the resolution image can be lowered.
On the other hand, there has been proposed an apparatus for developing the latent image formed on the photoconductor and transferring the developed image to an intermediate transfer body having a silicon rubber layer, and then transferring the transferred image onto a medium to be printed, which medium will be hereinafter referred to as a “printing medium”. However, such apparatus requires a large amount of heat energy for transferring and fixing the image. Also, the heat inherently elevates the temperature of the photoconductor via the intermediate transfer body, and thus the characteristics of the photoconductor may possibly be degraded.
A conventional cleaning mechanism of an image forming apparatus will be discussed in detail with reference to FIG.
6
.
FIG. 6
is a side elevation showing the first prior art disclosed in Japanese Unexamined Patent Publication No. Showa 62-286082. In
FIG. 6
, an intermediate transfer body
503
is in belt form which is formed by coating a surface of a rigid roll of stainless or the like with a silicon rubber or the like.
The intermediate transfer body
503
is clamped between a cleaning roll
501
heated by an internal heater and a pressure roll
507
positioned in opposition to the cleaning roll
501
and is fed therethrough. Thus, a residual toner
508
on the intermediate transfer body
503
is melted by the cleaning roll
501
and deposits thereon. On the cleaning roll
501
, a cleaning blade
504
which is formed with a thin plate of stainless steel or phosphor bronze, is contacted under pressure exerted by a spring
505
for removing the toner depositing on the surface thereof. The toner thus scraped is received in a waste toner box
509
. On the other hand, in order to prevent the waste toner from scattering, a sheet
506
formed with a heat resistant resin film, such as polyimide film or the like, is urged onto the cleaning roll
501
.
The toner on the intermediate transfer body
503
is softened to a certain extent by heat and pressure applied from the cleaning roll
501
. Furthermore, since a surface free energy of the surface of metal is greater than that of the silicon rubber, softened toner is efficiently deposited on the surface of the metal of the cleaning roll
501
. Furthermore, the softened toner is removed by pressure after passing through a nip portion between the cleaning roll
501
and the pressure roll
507
to be quickly hardened to be easily removed by the metallic cleaning blade
504
.
One employing a cleaning belt in place of the cleaning roll
501
for removing residual ink or stains or dirt on the surface of the transfer body may possibly cause fluctuations in pressure when the cleaning belt contacts the transfer body. Also, for low absorbing speed ink, fluctuation may be caused in removal of residual ink or stains or dirt on the surface of the transfer body to form a stain on the printed product.
FIGS. 7A and 7B
are a perspective view and a side elevation of the second prior art disclosed in Japanese Unexamined Patent Publication No. Heisei 04-016978, for example.
A cleaner
613
is constructed with a cleaning puff
610
, a cleaning roll
622
and a take-up roll
631
. A cleaning agent supplier
609
is formed with a plurality of conduits or one or more grooves to impregnate a cleaning agent stored therein into the cleaning puff
610
. The impregnating method of the cleaning agent in the cleaning puff
610
may be capillary force, a pressure difference between inside and outside of the cleaning agent supplier
609
, difference of concentration of the cleaning agent, heating by an electric heater, ultrasonic vibration or pumps.
The cleaning puff
610
impregnated with the cleaning agent is pressed onto a photoconductor drum
606
by the cleaning roll
622
in the vicinity of an ink absorbing portion
620
. The cleaning puff
610
absorbing contaminants is taken up by the take-up roll
631
. After absorbing contaminants, the cleaner
613
may rewind the almost dried cleaning puff
610
to the cleaning agent supplier
609
for reuse. Furthermore, when the same image is to be printed for a plurality of sheets simultaneously, cost may be saved by performing cleaning at a given interval or by reducing the impregnating amount of the cleaning agent.
The cleaning puff
610
may be formed with fabric paper, cloth, or plastics. However, by containing metallic or ceramic fiber, removal of static electricity or removal of solid deposits may be expected. On the other hand, the cleaning puff
610
may be formed from a porous sheet or sheet working into a particular pattern.
The cleaning agent is made of a material which may solve an ink to be used for printing. For example, in case of water soluble ink, a mixture prepared by adding a surface active agent and an antioxidant to solution of higher alcohols or glycol esters is taken as a primary component. In addition, depending upon composition of the ink, amines, ethyl's or other esters may be used.
On the other hand, when a dispersion type ink which is prepared by dispersing a pigment into a liquid component, a solvent having the same polarity as the dispersed particle or solvent easily solving the pigment may be used.
The conventional cleaning mechanism of the image forming apparatus set forth above employs the roll form cleaning means. The conventional roll type cleaning means merely removes the residual ink on the intermediate transfer body by coating the ink component on the roll for removing the ink utilizing the fact that binding power between the ink component on the cleaning roll and the residual ink on the intermediate transfer body is greater than that between the residual ink and the surface of the intermediate transfer body. However, on the surface of the cleaning roll, impurities other than the ink, substances contained in the ink component and degrading transfer performance, paper dust from the printing paper and so forth may deposit to lower cleaning performance. On the other hand, even assuming that the substance deposited on the surface of the cleaning roll is only ink, the ink amount is not uniform over the axial direction of the roll in some images. This forms irregularities on the surface of the cleaning roll and causes a loose fit between the cleaning roll and the intermediate transfer body resulting in cleaning failure.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a cleaning mechanism for an image forming apparatus which can assure stable cleaning performance, and constantly maintain surface conditions of an intermediate transfer body and a photoconductor to obtain sat
Fuji 'Xerox Co., Ltd.
Royer William J.
Young & Thompson
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