Cleaning device for cleaning an image bearing member with developer

A cleaning device for removing excess developer which remains on the image bearing member of an image formation apparatus after transfer of a developed image has a conveyor for conveying developer to a position which faces the image bearing member, and a device for bringing the conveyed developer into contact with the surface of the image bearing member to effect cleaning.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a cleaning device, and more particularly to a 
cleaning device in an image formation apparatus in which a magnetic 
developer image is formed on an endlessly moving image bearing member and 
transferred to a transfer medium, whereafter the surface of the image 
bearing member is cleaned for reuse. 
2. Description of the Prior Art 
In various types of image formation apparatus such as image formation 
apparatus in which an electrostatic latent image is formed on an image 
bearing member such as an electrophotographic photosensitive medium and 
developed and transferred and image formation apparatus in which a 
magnetic latent image is formed on a magnetic recording medium and 
developed and transferred, the image bearing member is cleaned for 
repetitive utilization. 
As the cleaning device for the image bearing members of these image 
formation apparatus, the fur brush system, the web system, the magnetic 
brush system or the blade system has heretofore been put into practical 
use. 
Dust, tobacco smoke, etc. in the environment adhere to the surface of the 
image bearing member of the image formation apparatus and impregnant or 
the like of the transfer medium also adheres thereto. These adhering 
materials cannot always be removed satisfactorily by the conventional 
cleaning systems. Moreover, if deterioration of the image bearing member 
progresses due to the action of corona ions or the like, it adversely 
affects the image formation. 
For the purpose of removing such adhering materials, it has been proposed 
to apply a polishing action to the surface of the image bearing member. 
Specifically, the polishing action is effected by polishing means 
comprising a polishing member such as polishing cloth slidably disposed at 
a position subsequent to the cleaning means or by polishing means provided 
with a mechanism for supplying a polishing agent to the surface of the 
image bearing member and a mechanism for causing the polishing agent to 
frictionally contact the surface of the image bearing member. However, 
where exclusive an polishing means is provided, there has been required 
space to accommodate the polishing means within the image formation 
apparatus and it has been necessary to add a complex mechanism. This 
provides a hindrance particularly in making the image formation apparatus 
compact. 
The present invention has been made in view of the above-noted point. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a novel and excellent 
cleaning device. 
It is another object of the present invention to provide a cleaning device 
which can maintain a uniform frictional contact effect. 
The device of the present invention is a cleaning device in an image 
formation apparatus in which a magnetic developer image is formed on an 
endlessly moving image bearing member and transferred to a transfer 
medium, whereafter the surface of the image bearing member is cleaned for 
reuse, characterized by cleaning means bearing against the surface of the 
image bearing member, catching and conveying magnetic means disposed 
upstream of the bearing position of the cleaning means in the direction of 
movement of the image bearing member, and a scraper member serving to heap 
up the magnetic developer on the catching and conveying magnetic means 
toward the image bearing member. 
With the above-described construction, developer is brought into frictional 
contact with the surface of the image bearing member before the cleaning 
member acts, thereby enabling the removal of adhering materials which has 
been difficult with the conventional systems. It is effective to mix a 
polishing agent with the developer as required. Moreover, the developer 
can be supplied to the surface of the image bearing member before the 
cleaning member acts and therefore, even if the developer partly adheres 
to the surface of the image bearing member after the image transfer, the 
developer can be uniformized and a uniform frictional contact action is 
enabled by the cleaning member. Incidentally, where non-uniform residual 
developer is frictionally removed by the cleaning member, the force 
applied to the portion of the cleaning member which bears against the 
image bearing member has become non-uniform in accordance with the 
condition of the developer adhering to the image bearing member. Creation 
of the partial concentration of pressure is liable to cause abrasion or 
damage of the image bearing member and is also liable to result in 
unsatisfactory cleaning. However, with the construction of the present 
invention, a uniform force is dispersed over the entire portion of the 
cleaning member which bears against the image bearing member, whereby the 
abovenoted problems are eliminated. 
Particularly, in the case of the so-called counter blade system in which an 
elastic cleaning blade is disposed so that the edge thereof opposes the 
direction of movement of the image bearing member, the above-described 
effect is more pronounced. At the position whereat the cleaning member 
bears against the image bearing member, the cleaning member not only 
blocks the passage of the developer on the image bearing member and 
separates the developer from the image bearing member but also enables 
more complete removal of the adhering materials to be accomplished by the 
frictional contact operation of the cleaning member resulting from the 
cooperation thereof with the developer. 
Other objects, features and operational effects of the present invention 
will become apparent from the following detailed description of specific 
embodiments of the invention taken in conjunction with the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a side view illustrating an image formation apparatus to which 
the device according to the present invention is applied. 
In FIG. 1, a photosensitive drum (image bearing member) 1 has the memory 
thereon removed by a pre-discharging corona discharger 2, whereafter it is 
uniformly charged by a primary cornoa discharger 3 and is subjected to 
secondary discharging by a corona discharger 4 while, at the same time, it 
is exposed to an image light 5 corresponding to an original, whereby an 
electrostatic latent image is formed on the photosensitive drum 1, 
whereafter the latent image is developed into a toner image by a 
developing device 6 using magnetic developer (toner). The toner image is 
transferred to a transfer medium, supplied from rollers 7 through a guide 
8, by a corona opposite in polarity to the toner and imparted to the 
transfer medium from the back side thereof by an image transfer corona 
discharger 9. The transfer medium having the copy image transferred 
thereto is separated from the photosensitive drum by separating means such 
as a separating roller 10, and is conveyed to fixing means, not shown. 
On the other hand, the photosensitive drum has any residual toner on the 
surface thereof removed by a cleaner 14 and is used repetitively. The 
conventional cleaner 14 shown comprising a cleaning blade 11 having its 
edge bearing against the surface of the photosensitive drum, a catching 
magnet roller 12 and a collecting screw 13. The magnetic toner removed by 
the blade 11 is caught by the magnet roller 12 and forms a toner brush on 
the surface of the magnet roller 12. The toner brush is maintained at a 
predetermined thickness by a scraper which serves also as a casing, and 
the excess toner is scraped and conveyed by the collecting screw 13. 
In the image formation apparatus of the described construction, foreign 
materials adhering to the drum surface from the transfer medium or 
substances produced by the corona discharge and adhering to the drum 
surface cannot be removed by the aforementioned cleaning blade, but rather 
form coatings which rigidly adhere to the drum surface, and these adhering 
films adsorb humidity particularly under a high humidity environment and 
reduce the surface resistance of the drum surface, thereby disturbing the 
latent image thereon. 
The polishing action by toner particles is effective for the removal of 
these foreign materials and particularly, if polishing powder such as 
cerium oxide is mixed with the toner, the effect will be greater. However, 
the amount of toner adhering to the drum surface depends on the original 
to be formed, and the amount of toner supplied to the blade portion is not 
constant. In an extreme case, if an original approximate to blank paper is 
continuously used, the toner or polishing powder accumulating on the blade 
portion will become almost null and the removal of the substances adhering 
to the drum surface by the polishing effect cannot be achieved. A latent 
image area for supplying toner may be provided outside the image area to 
ensure toner or polishing powder to be always supplied, but in such case 
the amount of toner consumed would be increased and the contamination of 
the interior of the apparatus would also be increased. 
FIGS. 2A and 2B illustrate the cleaning device 17 according to the present 
invention. FIG. 2A shows the cleaning device spaced apart from the 
photosensitive drum surface, and FIG. 2B shows the cleaning device 
installed at the photosensitive drum cleaning position. 
One end 16.sub.2 of a scraper member 16 is secured to the back side of the 
blade 11 of the cleaning device. The blade 11 has its edge portion formed 
of an elastic material such as rubber or synthetic resin. Alternatively, 
the entire blade may be formed of a suitable elastic material or, as 
shown, only the tip end portion of the blade may be formed of an elastic 
material and the support portion may be formed of a flexible metal such as 
phosphor bronze. When the blade 11 is spaced from the surface of the image 
bearing member (FIG. 2A), the free end 16.sub.1 of the scraper member 16 
is spaced apart from the magnet roller, but when the blade 11 is in a 
condition in which it is installed at the cleaning operation position 
(FIG. 2B), the free end 16.sub.1 of the scraper member 16 moves to a 
position in which it is in proximity or contact with the surface of the 
magnet roller 12 which faces the photosensitive drum. 
This scraper member 16, as shown in the cross-sectional view of FIG. 3 
which shows the scraper member with the blade and in the fragmentary front 
view of FIG. 4, has a plurality of openings 16.sub.3 provided in the 
central connecting portion leading from the free end 16.sub.1 of the 
scraper member to the blade mounting portion. 
Accordingly, when the magnetic developer caught and conveyed by the surface 
of the magnet roller 12 arrives at the position of the free end 16.sub.1 
of the scraper 16 which faces the photosensitive drum, the magnetic 
developer is heaped up from the roller surface by the free end 16.sub.1 of 
the scraper 16 to ensure the contact of the developer with the 
photosensitive drum surface. In this manner, the end of the heap of the 
magnetic developer and/or the polishing agent frictionally slides on the 
photosensitive drum surface and part thereof is replenished, whereby 
sufficient polishing cleaning is accomplished at the cleaning blade 
position. On the other hand, any developer remaining on the free end 
16.sub.1 of the scraper member circulates through the openings 16.sub.3 
provided in the connecting portion leading from the free end 16.sub.1 to 
the blade. 
The developer and/or the polishing agent removed by the cleaning blade also 
passed through the said openings and is caught and conveyed by the magnet 
roller surface. Any excess developer on the magnet roller surface is 
scraped off by a scraper (regulating member) 15 provided in the lower 
portion of the casing, whereby the thickness of the layer of developer on 
the magnet roller 12 is made constant. 
In this manner, stable supply of the developer and/or the polishing agent 
to the photosensitive drum surface is accomplished to provide a sufficient 
cleaning effect. 
FIG. 3 is an enlarged view of the neighborhood of the photosensitive drum 
of the apparatus shown in FIG. 2B. 
The magnet roller 12 is disposed on the bottom 17.sub.1 of the housing of 
the cleaning device 17 and in proximity to the photosensitive drum. The 
minimum clearance between the two is indicated as W. As mentioned 
hereinbefore, part of the collected developer is left on the magnet roller 
surface with a predetermined layer thickness t by the regulating member 15 
provided at the housing bottom 17.sub.1 and the circulation of such 
developer is utilized. The developer layer thickness t is set to a value 
somewhat smaller than the minimum clearance W between the surface of the 
photosensitive drum 1 and the magnet roller 12. (For example, t=0.7 mm for 
W=1 mm). By this, the heaping-up effect of the scraper member is 
sufficiently provided. On the other hand, the position of contact of the 
free end 16.sub.1 of the scraper member 16 with the magnet roller 12 is 
set so that the heap-up peak of the developer layer is a position 
exceeding the miminum clearance W. That is, the position of contact of the 
free end 16.sub.1 of the scraper member 16 lies in the area on the 
movement direction side of the magnet roller relative to the line passing 
through the centers of the magnet roller and the photosensitive drum. 
.alpha. is the angle formed between said line and a radial line from the 
center of the magnet roller to the position of contact. (.alpha.&gt;0) By so 
setting the scraper member 16, falling and scattering of scattered toner 
caused during the contact with the photosensitive drum surface at the 
heap-up peak of the developer layer may be prevented. That is, for 
example, even if scattered toner is created on the peak, the toner is 
required to pass through the narrowest portion between the magnet roller 
and the photosensitive drum and therefore, the toner is again caught by 
the magnet roller surface. Accordingly, there is no possibility that toner 
leaks from between the housing bottom 17.sub.1 of the cleaning device and 
the photosensitive drum. 
When the developer layer is to be heaped up by the scraper member, it is 
necessary that sufficient heap-up be formed and the peak of the heap-up 
keeps sufficient contact with the photosensitive drum surface. 
In order to set the amount of this heap-up as desired, it is effective to 
prescribe the width A of the free end 16.sub.1 portion of the scraper 
member, namely, the length from the free end 16.sub.1 to the lower end of 
the opening 16.sub.3 (see FIG. 5), to a suitable condition. By making this 
width A sufficiently great, the amount of heap-up can be increased and the 
peak thereof can also be heightened. On the other hand, if the width A is 
decreased, the amount of heap-up can be decreased and the peak thereof can 
also be lowered. For example, where a Mylar (trade name) sheet having a 
thickness of 100.mu. is used as the scraper member, if the width A is 1.5 
mm or greater in the shown arrangement, there will be obtained a 
sufficient heap-up which will act on the photosensitive drum surface. At 
this time, the minimum clearance W=1.0 mm and the developer layer 
thickness of t=0.7 mm. 
A non-magnetic material is required as the scraper member, and a desired 
material such as a metal sheet of phosphor bronze or stainless steel or 
synthetic resin such as Mylar may be chosen for the scraper member. 
However, where the scraper member is disposed in the narrow space between 
the magnet roll and the photosensitive drum as in the device shown, the 
shown example of the sheet-like member is suitable for the setting of the 
amount of heap-up. For example, in the case of Mylar, 50.mu. or greater 
would be sufficiently practical. In the case of a metal sheet or the like 
having high flexibility and strength, the thickness of the sheet may be 
smaller. 
On the other hand, in the case of a material of weak strength, the sheet 
thickness of the scraper member itself may be made great and the free end 
thereof may be formed into a wedge-like shape. 
In the above-described specific example of the device, the scraper member 
is fixed to the blade so as to be operatively associated with the latter, 
but the scraper member may of course be provided independently of the 
cleaning means. However, where the scraper member is operatively 
associated with the cleaning member is shown in the specific example, the 
following effect is obtained. 
In case of the so-called counter arrangement in which the blade is disposed 
in a direction counter to the direction of movement of the photosensitive 
drum as shown, when supplied with excessive developer and/or polishing 
agent, the wedge-shaped space defined by the blade edge portion and the 
photo-sensitive drum surface is filled with developer and a great 
compression force is applied to the blade itself to cause it to move along 
the direction of movement of the photosensitive drum. In response thereto, 
the scraper member also moves and therefore, the free end of the scraper 
member becomes spaced apart from the magnet roller surface and the heap-up 
of developer is decreased. Therefore, the amount of developer supplied to 
the cleaning station is decreased, so that the filling rate of the 
wedge-shaped space with developer is alleviated to provide a suitable 
amount of developer. On the other hand, where the amount of developer 
supplied to the wedge-shaped space is small, the compression force applied 
to the blade is decreased and the blade itself becomes stretched in a 
counter direction. At this time, the scraper member comes into its closest 
proximity or contact with the magnet roller surface to thereby provide a 
large heap-up of developer layer. Thus, the amount of developer supplied 
is increased, so that the filling of the wedge-shaped space of the blade 
with developer is promoted and a good cleaning force can be obtained for 
moderate compression. Thus, in the construction of the above-described 
specific example, the position of the scraper member can be very well 
prescribed so that the cleaning action of the cleaning blade may always be 
maintained suitable. 
The openings formed in the scraper member may be square shaped as shown in 
FIG. 5, but alternatively they may be circular as shown in FIG. 6. Of 
course, other shapes may also be adopted. 
Of course, the scraper member may be formed by punching a sheet-like body 
so as to provide openings therein, and a plurality of combtooth-like 
support lines may be studded on a band-like sheet corresponding to the end 
portion which acts on the magnet roller and the ends of the support lines 
may be fixed to the blade side. 
As described above in detail with respect to the specific example, the 
device of the present invention is an excellent one which displays a 
sufficiently good cleaning effect even in a case where adhering materials 
which could not be removed by the conventional cleaning means are present 
on the surface of an image bearing member such as a photosensitive drum.