Dry process developing apparatus

In a dry process developing apparatus, a seal member closes a gap between a photoconductive element and the upper end of a housing which has a developing roller, a toner supply roller and the like thereinside. A blade for regulating the thickness of a toner layer on the developing roller is spaced at its base end portion from the wall of the housing to set up a toner recirculation path. An oscillator plate extends generally downwardly to neighbor the toner supply roller at the free end thereof. The free end of the vibrator is caused into oscillation by a drive unit. The oscillator and drive unit cooperate to guide a toner dropped by a toner replenish device, which replenishes the toner to the housing, toward the toner supply roller.

BACKGROUND OF THE INVENTION 
The present invention relates to a dry process developing apparatus for use 
with an apparatus for electrophotography. 
An electrophotographic apparatus generally includes a developing apparatus 
for processing into a toner image a latent image which is 
electrostatically formed on a photoconductive drum by image light 
reflected from an original document. Among various apparatuses of the kind 
concerned, a dry process developing apparatus comprises a developing 
roller located to face the photoconductive drum between a charger and a 
transfer charger, a bladed toner supply roller positioned at the opposite 
side to the drum with respect to the developing roller in order to supply 
the toner to the developing roller, and a casing having the toner supply 
roller and developing roller thereinside and formed with an opening which 
faces the drum. Inside the casing, the toner is supplied from the toner 
supply roller onto the developing roller to form a magnet brush on the 
developing roller due to the attraction by a plurality of magnets 
installed in the developing roller. The magnet brush is brought into 
contact with the drum through the opening in accordance with the rotation 
of the developing roller. 
A problem has existed in this type of developing apparatus in that the fine 
toner particles tend to fly apart through the gap between the drum and the 
upper end of the opening of the casing as well as through the gap between 
the drum and the lower casing end. The leaked toner particles smear an 
imaging system, transfer unit and other arrangements located around the 
developing device, thereby degrading the image quality to a critical 
degree unless frequent services are effected. Particularly, the casing 
lower end and drum are usually spaced a certain distance large enough to 
prevent a toner image carried on the drum from being damaged, allowing a 
substantial amount of toner particles to leak through the spacing. This 
part of the toner smears a lamp for image transfer which extends along the 
axis of the developing roller, resulting in a change in the intensity of 
illumination by the lamp. Any inadequate intensity level of illumination 
would effect the quality of reproduced images. Additionally, the toner 
dropping along the drum contaminates the transfer charger or a sheet guide 
and, as a result, renders the effect of the transfer charger uneven in the 
lengthwise direction while smearing sheets fed along the sheet guide. 
The toner leakage described above becomes particularly prominent in the 
case of a two-component magnetic toner. When the toner is uncoupled from 
the carrier while being routed through various paths during development, 
fine particles thereof are made afloat. 
Meanwhile, the developing apparatus of this type has a toner supply device 
which is located in an upper portion thereof. It is desirable that the 
toner fed downwardly from the toner supply device be caused to drop 
directly on the toner supply roller. However, the current tendency is to 
space the toner supply device as much as possible from the drum in the 
horizontal direction due to various layout limitations. For example, 
because the toner supply device which includes a toner container occupies 
a substantial space, it has to be located to avoid its interference with 
the imaging system. 
Therefore, the toner from the container drops not on the toner supply 
roller but on the casing adjacent to the toner supply roller. As the time 
elapses, the toner dropping on the casing forms a heap. It is not until 
the heap of toner slides down that the toner is scooped into the gap 
between the blades of the toner supply roller and thereby fed to the 
developing roller. A certain period of time, therefore, expires before the 
toner is actually supplied by the toner supply roller to the developing 
roller. Should the development occur within this "transitional" period of 
time, the resulting image would be poor quality due to the short supply of 
toner. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a dry process 
developing device which insures a constant quality of image reproduction 
without any contamination. 
It is another object of the present invention to provide a dry process 
developing apparatus which prevents toner particles from flying off to the 
outside of the casing. 
It is another object of the present invention to provide a dry process 
developing apparatus which in an apparatus for electrophotography protects 
various units therearound against contamination by the toner. 
It is another object of the present invention to provide a dry process 
developing apparatus which shortens the transitional time in the toner 
supply while eliminating incomplete development. 
It is another object of the present invention to provide a generally 
improved dry process developing apparatus. 
In one aspect of the present invention, there is provided a dry process 
developing apparatus for processing an electrostatic latent image formed 
on a photoconductive element into a toner image. A housing is formed with 
an opening which faces the photoconductive element. A magnet brush forming 
member is positioned in the vicinity of the opening to form a magnet brush 
of a toner. A seal member seals a gap between the upper end of the opening 
of the housing and the photoconductive element, whereby leakage of the 
toner through the gap is prevented. 
In another aspect of the present invention, there is provided a dry process 
developing apparatus for processing an electrostatic latent image formed 
on a photoconductive element into a toner image. A housing has thereinside 
a magnet brush forming member which forms a magnet brush of a toner. A 
toner supply member supplies a toner to the magnet brush forming member. A 
toner replenish device is formed with an opening for replenishing the 
toner to the toner supply member. An oscillator member applies oscillation 
to the toner in the toner replenish device which is guided to the toner 
supply member via the toner supply opening. A drive means drives the 
oscillator member. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following detailed description 
taken with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
While the dry process developing apparatus of the present invention is 
susceptible of numerous physical embodiments, depending upon the 
environment and requirements of use, substantial numbers of the herein 
shown and described embodiments have been made, tested and used, and all 
have performed in an eminently satisfactory manner. 
To facilitate understanding of the present invention, a brief reference 
will be made to a prior art apparatus for dry process development, 
depicted in FIG. 1. The apparatus generally designated by the reference 
numeral 10 is located to face a photoconductive drum 12 and between a 
charger 14 and a transfer charger 16, which are arranged around the drum 
12. The drum 12 is rotatable as indicated by an arrow A during operation 
of the apparatus. A developing roller 18 comprises a cylindrical sleeve 
18a and a group of magnets 18b fixed in position within the sleeve 18a. 
The sleeve 18a is rotatable relative to the magnet group 18b so that its 
part facing the drum 12 may move in the same direction as the drum 12, 
i.e., in the direction indicated by an arrow B. The magnet group 18b 
comprises a main pole 18b.sub.1 which contributes to the development in 
the developing region by raising a nap of a toner on the sleeve 18a, and 
four auxiliary poles 18b.sub.2 -18b.sub.5 at spaced locations along an 
imaginary circle K which passes through the main pole 18b.sub.1. The 
auxiliary poles 18b.sub.2 -18b.sub.5 are adapted to convey the toner on 
the sleeve 18a. 
A toner supply roller 20 faces the developing roller 18 and comprises 
either a magnetic roller as the developing roller 18 or a roller having a 
number of radially extending blades as illustrated. The bladed roller will 
scoop the toner into the gaps between its blades and supply it to the 
developing roller 18 as it is rotated as indicated by an arrow C. 
Both the developing roller 18 and toner supply roller 20 are installed in a 
housing 22 which is open at its portion which opposes the drum 12. The 
housing 22 is also open at its upper part located to the right and above 
the roller 20 and communicated thereat to a container 24 which stores a 
fresh supply of toner T thereinside. The toner T is fed from the container 
24 toward the roller 20 in accordance with the rotation of a roller 24a. 
The toner T is replensished from a hopper 26 into the container 24 and 
constantly agitated therein by an agitator 28. The container 24, roller 
24a, hopper 26 and agitator 28 constitute in combination a toner replenish 
device 30. 
The toner T fed by the roller 20 onto the sleeve 18a forms a magnet brush 
under the attraction by the magnet group 18b. The magnet brush moves 
toward the drum 12 together with the sleeve 18a while the height of its 
nap is regulated by a blade 32. A separator 34 is positioned above the 
rollers 18 and 20 in order to control the flow of the toner within the 
housing 22. 
An exposure station 36 is located between the developing apparatus 10 and 
the charger 14. Image light reflected by a document is passed through an 
imaging system 38 to the exposure station 36. A latent image thus formed 
electrostatically on the drum 12 is developed by the apparatus 10 into a 
toner image. The toner image is illuminated by a lamp 40 to have its 
adhesion to the drum 12 weakened to a level suitable for transfer and, 
then, transferred onto a sheet of paper while passing through the transfer 
charger 16. 
The present invention is successful to preclude the leakage of the toner 
through the gaps between the drum and the upper and lower ends of the 
adjacent opening of the housing, which has been the drawback inherent in 
the prior art developing apparatus as previously discussed. 
Referring to FIG. 2, a dry process developing apparatus embodying the 
present invention is shown. In FIG. 2, the structural elements common to 
those shown in FIG. 1 are designated by like reference numerals. A 
characteristic feature of the illustrated embodiment is that a first seal 
member 50 is employed to prevent the toner from being scattered through 
the gap between the drum 12 and the upper end of the housing 22. The seal 
member 50 is firmly nipped by a bent plate member 52 which is rigidly 
mounted on the underside of an upper portion 22a of the housing 22. Thus, 
the gap between the housing upper end 22a and the drum 12 is closed by the 
seal member 50. It is a primary requisite that the seal member 50 be made 
of a material which is electrically insulating to be prevented from 
disturbing a latent image on the drum 12 and is hardly chargable even 
under frictional contact with the drum 12. Concerning the insulation, for 
example, a film or a brush is suitable which is made of insulating 
filaments of the kind which exhibits a resistance of 10.sup.9 .OMEGA. or 
more when engaged with the drum 12 over the width of 300 mm, e.g. 
fluorine-contained resin. A desirable example is a brush made of Teflon. 
The filaments which form the brush should be soft and have a diameter 
within the range of about 50-200 microns. The effective design of such a 
brush may be such that the filaments are arranged to a density of about 
20,000 /cm and allowed to flex over about 1 mm in contact with the drum 
and throughout the width of the drum while following the rotation of the 
drum. 
Another characteristic feature of the apparatus of the present invention is 
that a second seal member 54 is located at a lower end 22b of the housing 
22. The seal member 54 is secured at one end to the housing lower end 22b 
and extends along the rotating direction of the sleeve 18a such that the 
other end thereof faces the auxiliary pole 18b.sub.2 and contacts the 
sleeve 18a or the toner on the sleeve 18a. The seal member 54 extends in 
the axial direction of the sleeve 18a. Preferably, the seal member 54 
comprises a brush having acrylic or like soft filaments which are about 7 
mm in the length of their free portion and 20,000-30,000 per square inch 
in density. 
The toner on the sleeve 18a is adhered thereto by the magnetic field 
developed by the main pole 18b.sub.1 and, in the developing region, the 
nap of the magnet brush is raised to stroke the latent image on the drum 
12. The nap between the main pole 18b.sub.1 and the auxiliary pole 
18b.sub.2 is laid down but becomes raised again as soon as it enters the 
zone where the magnetic field of the auxiliary pole 18b.sub.2 is strong. 
At this instant, the toner carried by the end of the nap tends to separate 
therefrom and the separated part of the toner falls down through the gap 
between the housing lower end 22b and the drum 12, bringing about the 
problem particular to the prior art apparatus. In accordance with the 
present invention, when the nap is raised as indicated by Q in FIG. 2 on 
the sleeve 18a adjacent to the auxiliary pole 18b.sub.2, the second seal 
member 54 checks the toner at a position ahead of the raised nap Q with 
respect to the rotating direction of the sleeve 18a. Therefore, major part 
of the toner separated from the nap is captured by the seal member 54 and 
thereby prevented from flying apart to the outside of the casing 22. 
The brush exemplifying the seal member 54 is kept in light contact with the 
toner having the nap laid down, so that the toner separated from or about 
to be separated from the nap is caught. Where the brush 54 is located very 
close to the auxiliary pole 18b.sub.2 in contact with the sleeve 18a, it 
will capture the toner immediately before or after the separation due to 
the rise of the nap. On the other hand, where the brush 54 is positioned 
adjacent to the main pole 18b.sub.1 in contact with the sleeve 18a, it 
will check the toner which is separated from the raised nap and flying 
toward the outside. 
As the operation of the developing apparatus 10 is repeated, the toner 
caught by the brush 54 may be progressively accumulated thereon. This 
problem can be settled by suitably designing the filament density of the 
brush 54 and selecting a soft material for the filaments. The same may be 
further implemented by selecting a material for the brush which 
approximates to the toner in charge characteristics, because such a 
material will hardly allow electric attraction to develop between the 
toner and the brush. While a brush yielded a favorable result in 
experiments, it may be replaced by a soft film-like elastic member without 
effecting the sealing effect. 
The toner cloud due to the raised nap, apart from the position of the 
sleeve 18a corresponding to the auxiliary pole 18b.sub.2, occurs also in a 
position corresponding to the auxiliary pole 18b.sub.5 or as a result of 
an impact of the toner T on the drum 12 at the inlet of the developing 
region. The seal member 50 located in this position as already mentioned 
catches the toner separated by the raised nap, thereby maintaining the 
apparatus 10 clean more efficiently. 
While effectively sealing the casing 22, the first and second seal members 
cause the air pressure inside the housing to rise due to the sealing. The 
elevation of the internal pressure of the housing 22 might allow the toner 
to leak through the gap between the drum 12 and the housing lower end 22b. 
Because the toner image carried on the drum 12 has to be protected against 
damage, it is impossible to dispose a strict sealing means between the 
drum 12 and the housing lower end 22b; a simple member of urethane rubber 
having an undulated surface is located in the vicinity of the drum 12. 
Still, the toner forms a magnet brush T.sub.1 between the drum 12 and the 
sleeve 18a in the intermediate between the opposite ends of the drum 12 as 
illustrated in FIG. 3. The magnet brush T.sub.1 functions to seal the 
housing lower end 22b against the leakage of the toner therethrough. 
The toner leakage is also liable to occur at axially opposite ends of the 
developing roller 18 through gaps t.sub.1 and t.sub.2 shown in FIG. 3. The 
gap t.sub.1 corresponds to a flange 60 which is rotatable integrally with 
the sleeve 18a but lacks a magnet and, therefore, magnetic attraction. The 
toner, therefore, does not form any nap and part of the toner let fall 
through the gap t.sub.1 moves along the surface of the drum 12 to drop on 
part of the lamp 40 via the gap between the housing 22 and the drum 12, 
thereby smearing opposite end portions of the lamp 40. This makes the 
illumination intensity distribution of the lamp uneven along the length 
thereof and, therefore, results in an uneven transfer of the toner image 
onto a sheet. Additionally, the leaked toner smears the transfer charger 
16 as well as a sheet guide (not shown), so that the effect of the 
transfer charger 16 becomes uneven along the length thereof and sheets 
become smeared. The gap t.sub.2, on the other hand, is defined between the 
axial end of the flange 60 and the adjacent end of the housing 22. The 
toner dropping through this gap t.sub.2 is as undesirable as the toner 
dropping through the gap t.sub.1. 
The toner leakage through the gaps t.sub.1 and t.sub.2 results from the 
fact that the pressure inside the hermetic space defined by the housing 
22, developing roller 18, drum 12, seal members 50 and 54 and the like is 
elevated during the course of repeated rotation of the drum 12 and roller 
18, blowing air out through the gaps t.sub.1 and t.sub.2 which may be 
regarded as a single outlet of the hermetic space. 
Another characteristic feature of the illustrated embodiment is that, 
besides the seal members 50 and 54, a flat blade 70 is mounted integrally 
to the side walls of the casing 22 through a shaft 74 which extends 
throughout a base portion of the blade 70. The base portion of the blade 
70 is spaced a predetermined distance from the top of the housing 22, so 
that a toner recirculation path 72 is defined at the back of the blade 70. 
The recirculation path 72 assists the gaps t.sub.1 and t.sub.2 as a second 
opening of the hermetic space concerned, which lowers the internal 
pressure of the hermetic space and thereby checks the toner which tends to 
leak through the gaps t.sub.1 and t.sub.2. The recirculation path 72 
allows the toner to flow as indicated by phantom lines in FIG. 2. As 
shown, air entraining the toner flows through the path 72 to the outside 
and this, coupled with the pressure loss in the path 72 which is 
predetermined to be smaller than that in the gaps t.sub.1 and t.sub.2, 
eliminates the toner leakage through the gaps t.sub.1 and t.sub.2. 
Referring to FIGS. 4 and 5, another embodiment of the present invention is 
shown which employs a generally L-shaped blade 80 for defining a modified 
toner recirculation path 82. As shown, the blade 80 has an extension 84 
which extends in parallel with the top wall of the housing 22 as far as a 
position above the toner supply roller 20. The extension 84 is formed with 
openings 86 therethrough. With this construction, the recirculation path 
82 comprises the space defined between the casing 22 and the blade 
extension 84 and the opening 86 of the blade extension 84. The openings 86 
may be dimensioned and shaped as desired insofar as its position is 
optimum for the agitation of the recirculated toner, which is immediately 
above the separator 34 in this embodiment. 
Dropping the recirculated toner in the position remote from the roller 18 
is also advantageous in the following respects. If the recirculated toner 
is dropped in the vicinity of the roller 18, it will be reused for 
development under the fatigued condition and by a substantial proportion 
relative to fresh one. Thus, the toner dropped at a position remote from 
the roller 18 will be mixed with a fresh supply of toner to form a 
composition which is desirable for development. Meanwhile, if the drop 
point of the recirculated toner neighbors the roller 18, a large amount of 
toner will be dropped by gravity to possibly leak through the gaps t.sub.1 
and/or t.sub.2. This possibility is eliminated by the construction shown 
in FIG. 4. The dimensions, shape, pitch and others of the openings 86 may 
be varied to control the distribution of the toner within the casing 22 as 
desired. 
Furthermore, the blade 80 is supported at as many as four positions 90, 92, 
94 and 96 at the front and rear ends thereof. This implements the means 
indispensable for firmly and accurately retaining a blade of the kind 
concerned which regulates the thickness of a magnet brush by stroking the 
brush which is adhered to a roller under strong magnetic attraction. 
Still another embodiment of the present invention will be described with 
reference to FIGS. 6 and 7. As shown, the apparatus includes an oscillator 
plate 100 made of a material which is resilient and sparingly gathers 
rust, e.g. phosphor bronze or stainless steel. The oscillator plate 100 
has a base end 100a which is rigidly nipped between the upper end of the 
housing 22 and the lower end of the container 24. The base end 100a 
connects to a flat extension 100b which is bent generally downwardly 
toward the toner supply roller 20 across the toner drop path. The 
lowermost or free edge of the extension 100b is positioned quite close to 
the periphery of the roller 20 as illustrated. Legs 100c and 100d extend 
from the opposite ends of the extension 100b to have the roller 20 
therebetween. Pins 102a and 102b (only the pin 102a is visible) are 
studded on the opposite side walls of the roller 20 so that they may 
interfere with the oscillator legs 100c and 100d, respectively. 
As the roller 20 is rotated in the direction C in FIG. 6, the pins 102a and 
102b rotating with the roller 20 urge their associated legs 100c and 100d 
upwardly. The engagement of the pins 102a and 102b with the oscillator 
legs 100c and 100d is automatically released in due course so that the 
oscillator 100 springs back to the original position. Such successive 
actions of the oscillator 100, particularly the snap to the original 
position, causes the toner deposited on the extension 100b to hop into the 
gap between the blades of the roller 20. As a result, the dropping toner 
is not accumulated in the space F but caught by the oscillator extension 
100b and then forcibly fed to the toner supply roller 20 by the 
oscillation. This has the effect of remarkably shortening the transitional 
time period in the supply of toner to the developing roller 18. While the 
means for oscillating the oscillator 100 has been shown and described as 
comprising the legs 100c and 100d and the pins 102a and 102b, it may be 
replaced by a solenoid or the like which causes the oscillator into 
oscillation at a predetermined frequency. If desired, two or more pins may 
be studded on each side of the roller 20 at circumferentially spaced 
locations in due consideration of the expected amount of the dropping 
toner; the larger the number of the pins, the larger the frequency of 
oscillation of the oscillator 100 becomes. It will be noted that each 
oscillator leg 100c or 100d may be curved as illustrated in FIG. 6 in 
order to promote smooth movement of the pin 102a or 102b into and out of 
contact with the leg 100c or 100d. 
In accordance with the present invention, there is eliminated the design 
restriction that the toner supply device 30 and toner supply opening 
should be located immediately above the toner supply roller, so that the 
toner can be supplied within a shorter period of time than in the prior 
art apparatus. 
Various modifications will become possible for those skilled in the art 
after receiving the teachings of the present disclosure without departing 
from the scope thereof.