Developing device

An apparatus for electrostatic latent image development having two or more units for multicolor development provided around a photoreceptor. Each unit has a developer feed controller for feeding developer to the developing section having a developing roller facing the photoreceptor drum and for shutting off the feeding and has a doctor blade in the feed up-stream in turning direction of the developing roller. Developer is applied to the developing section when development is performed by displacement of the developer feed controller and is shut off when the developing unit is not used for development.

FIELD OF THE INVENTION AND RELATED ART STATEMENT 
This invention relates to a developing device for electrostatic latent 
images on the photoreceptor of electrostatic copying machines and others, 
particularly the device having two or more developing units for multicolor 
development arranged around periphery of the photoreceptor. 
Each developing unit of such developing device is provided with a 
developing roller to apply developer onto the photoreceptor. It is 
necessary to design such developing device so that the developing unit 
containing the developer for a required color is used and to keep the 
other units off the developing. If the developer is supplied to the 
developing roller of the units kept off the developing, unnecessary 
developer is deposited onto the photoreceptor, which makes the print 
quality lower. Various kinds of compositions have been proposed to prevent 
this. 
The Official Gazzette of Japanese Patent Publication unexamined No. Sho. 
54-109946, for example, shows a composition to control supply of developer 
to the developing roller by turning a magnetic roller provided in a rotary 
sleeve of the developing roller of the unit at non-developing by certain 
angle. In this case, however, it is necessary to provide a magnetic roller 
which turns as required in the rotary sleeve turning at a constant speed, 
which makes the composition very intricated. 
By another contrivance, as shown in the Official Gazzette of Japanese 
Patent Publication unexamined No. Sho. 55-169160, supply of developer onto 
the photoreceptor is prevented by providing a developer scraping blade to 
prevent deposition of developer onto the developing roller near the 
developer outlet and in a manner so that the blade swings freely and apart 
from the scraper provided to scrap off the developer on the circumference 
of the developing roller after developing and by putting the top end of 
the scraping blade of the developing unit at non-developing in contact 
with periphery of the developing roller. 
With a developing device of this composition, however, the developer 
scraped off by the blade is accumulated under the developing roller. As 
the developing roller turns, the accumulated developer is compressed 
causing block of toner and making deterioration of the carrier easier. 
It happened, in some cases, that the developer is splashed around when the 
blade is separated from the developing roller and leaks out of the 
developing device through the opening for developing. 
OBJECT AND SUMMARY OF THE INVENTION 
In view of the foregoing this invention is to provide a developing device 
of simple composition, which can prevent the developer from being supplied 
to the developing roller of the developing unit at non-developing so that 
unnecessary developer may not be deposited onto the photoreceptor and that 
the print quality may not be lowered, and can prevent blocking of toner 
and deterioration of carrier. 
To realize the object, the developing device of the invention is provided 
with a developer feed control means to supply developer to the developing 
unit or to shut off the supply so as to move within the range which does 
not come in contact with the developing roller and at the developer feed 
unit positioned at the upper stream side than the doctor blade of each 
developing unit in turning direction of the developing roller. At 
non-developing, supply of developer to the developing roller is prevented 
by operation of the feed control means.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 and FIG. 2 show the main part of an electrostatic copying machine 
provided with the developing device of the 1st embodiment of this 
invention. In FIG. 1, 1 is a photoreceptor drum on which electrostatic 
latent images are formed, and two or more number of developing units 2a, 
2b are arranged around the photorecepter drum 1, and developers of 
different colors are stored respectively in the housing of each developing 
unit 2a, 2b so that multicolor development of said electrostatic latent 
images is carried out. 
The housing of said developing units 2a, 2b is composed of a developing 
roller housing part 4 in which the developing roller 3 is housed, and of a 
developer housing part 6 in which the stirring roller 5 is housed, and 
developer made of toner and carrier is kept in the developer housing part 
6. 
Developing roller 3 is composed of a cylindrical rotary sleeve 7 driven in 
clockwise direction in the drawing by a driving mean not illustrated and 
of a magnetic roller 8 having N poles and S poles magnetically attached to 
two or more number of positions in the roller with certain spacing, and 
the developer is deposited onto the surface of the rotary sleeve 7 by the 
magnetic force of this magnetic roller 8 forming a magnetic brush. 
A doctor blade 10 to control thickness of the developer deposited onto the 
peripheral surface of the rotary sleeve of the developing roller is 
provided at the upstream side in turning direction of the developing 
roller 3 at the developing opening 9 of the housing. As the rotary sleeve 
7 turns, the magnetic brush moves to come in contact with the surface of 
the photorecepter drum 1 at the developing opening 9 made at the front 
side of the developing roller housing 4 so as to develop the electrostatic 
latent image. 
The area of the developing opening 9 of the developing roller 4 facing to 
the photoreceptor drum is the port for development. A toner hopper 11 is 
provided at the upper part of said developer housing unit 6, and the toner 
kept in the hopper is supplied through the feed roller 12 onto the 
stirring roller 5, then is carried to the developing roller housing 4 
while being mixed with the developer in the developer housing 6. 
Between the developing roller housing 4 at the developer feeder pistion at 
the up stream side of doctor blade 10, in the turning direction of the 
developing roller 3, and the developer housing 6, a scraper 13 is provided 
as shown in FIG. 2 to scrape the magnetic brush after development and to 
return the developer to the developer housing 6. 
Under the scraper, a control plate 14 acts as the developer supply control 
means to control the flow of the developer from the developer housing 6 to 
the developing roller housing 4. 
The control plate 14 is movable within the range of no contact with the 
developing roller 3 and is attached so as to swing freely around the 
rotary shaft 14a, and is so composed as to swing and move freely between 
the condition to flow developer and the condition to shut-off the flow 
through a lever 15 attached to the rotary shaft 14a, solenoid 16 
comprising the driving unit as a part of the developer feed control means, 
and a spring 17. 
When the solenoid 16 is not energized, the control plate 13 is held at 
inclined condition shown by continuous line by the tension of the spring 
17 and developer flow gap is opened. When the solenoid 16 is energized, 
the lever 15 turns against the tension of the spring 17, and the developer 
flow gap between the developing roller housing 4 and the developer housing 
6 is closed by the control plate 14 as shown by the phanthom line. To 
operate the copying machine of the above composition, the control plate 14 
of either one of the developing units 2a, 2b, 2b for example, containing 
the developer of the color used for developing is set at open position, 
and the control plate 14 of the other developing unit 2a is set at closed 
position. Accordingly, new developer is not supplied from the developer 
housing 6 to the developing roller housing 4 of the developing unit 2a 
containing the developer of the color not used for the developing, and the 
developer in the developing roller housing 4 is returned to the developer 
housing 6 through the developing roller 3 and the scraper 13. 
Consequently, the developer in the developing roller housing runs out. 
This prevents supply and deposition of unnecessary developer onto the 
surface of the photoreceptor drum 1 and also prevents the print quality 
from being lowered. 
The developer returned to the developer housing 6 is not subjected to any 
significant compression as is allowed to flow freely in the housing 6 
without staying at one place. This effectively prevents blocking of toner 
in the developer or deterioration of carrier due to breakage. As there is 
no need to provide any scraping blade to scrape off the developer besides 
the scraper 13, it doesn't happen that the developing roller 3 is damaged 
on the peripheral surface by the blade or that the developer is 
deteriorated being pressed against the developing roller. 
It is also possible to use driving means of prior art such as a stepping 
motor in place of said solenoid 16 as the driving unit to swing said 
control plate 14. To the developing device described in the above 
embodiment, the developer of two components comprising toner and carrier 
is used. The composition of this invention, however, is also application 
to a developing device using one component developer made of magnetic 
toner. The same is true with the examples of embodiments described in the 
following text. 
FIG. 3 shows the developing section of an electrostatic copying machine 
having two developing units 2a, 2b of the 2nd embodiment of this invention 
positioned vertically. 
Each one of said developing units 2a, 2b comprises a housing containing 
developer of two components of toner and carrier, a developing roller 3 
provided facing to the photoreceptor drum 1 on which electrostatic latent 
images are formed, a stirring roller 5 installed in parallel to the 
developing roller 3, and a scraper 13 to scrape toner after developing and 
provided above the stirring roller 5. Developers of different colors are 
housed respectively in the housing of the developing units 2a, 2b for 
multi-color development of the electrostatic latent image on the 
photoreceptor drum. 
The developing roller 3 is composed of a cylindrical rotary sleeve 7 turned 
by a driving means not illustrated in opposite direction to the 
photoreceptor drum 1, and a stationary magnetic roll 8 inside the rotary 
sleeve and having N and S poles fixed magnetically on the periphery with 
certain spacing. The developer is deposited by the magnetic force of the 
magnetic roller 8 onto the surface of the rotary sleeve 7 to form a 
magnetic brush. As the rotary sleeve 7 turns, the magnetic brush moves and 
comes in contact with the photoreceptor drum 1 at the opening for 
developing 9 of the housing to develop said electrostatic latent image. On 
the bottom of the housing, a doctor blade 10 is projected to control the 
height of the magnetic brush. 
The toner kept in the toner hopper at the upper part of the housing is 
supplied onto the stirring roller 5 through the feed roller 12, then is 
carried to the developing roller 3 while being mixed with the developer in 
the housing by the stirring roller 5. The developer carried by the 
stirring roller is deposited onto the surface of the rotary sleeve 7 to 
form a magnetic brush at the position corresponding to the N pole formed 
under the magnetic roller 8, i.e. at the developer feed section 20 
positioned at the up-stream side of doctor blade 10 in the turning 
direction of developing roller 3. 
A notch 21 is formed at a part of the bottom plate of the housing and in 
the range corresponding to the developing roller 3, and the notch 21 is 
covered with an elastic body 22 such as rubber plate. Under the elastic 
body 22, a magnet 24 as developer feed control means is placed facing to 
the developer feed section 20. As shown in FIG. 4 and FIG. 5, the magnet 
24 is supported by the pins 25, 25 projecting at both ends of the holder 
23 so as to turn freely and is turned by an operating means 27 comprising 
the solenoid as a part of the developer feed controller interlocked with 
the lever 26, which is inserted into the base of the holder 23. 
The holder 23 is turned around the pins 25, 25 by turning on and off the 
operating means 27 to move up and down the operating lever 28 of the 
solenoid and the magnet 24 falls down along the lower face of the elastic 
body 22 to change the position between the condition where the N pole at 
the top end is kept off the developer feed section 20 (see the developing 
device 2b at the lower part of FIG. 3) and the condition where the magnet 
24 rise to push up the elastic body 22 and the N pole at the top end comes 
close to the developer feed section 20 (see the developing device 2a at 
the upper part of FIG. 3). 
To operate a copying machine of the above composition, the magnet 24 of the 
developing unit containing the developer of the color used for the 
development is set at the above described off position from the developer 
feed section and the magnet 24 of the other developing unit is set at the 
close position to the developer feed section. By this setting, the 
magnetic drawing force of the developing roller at the developer feed 
section of the developing unit containing the developer of the color not 
used for the developing is lowered by the magnetic force of the magnet 24, 
and quantity of the developer deposited on the pheriperal surface of the 
developing roller 3 is greatly reduced. As the result, the magnetic brush 
is not formed to enough height to come in contact with the surface of the 
photoreceptor drum thus preventing lowering of the print quality due to 
deposition of the developer of the color not used onto the surface of the 
photoreceptor drum 1. 
When a part of the bottom plate of the housing is made of elastic body 22, 
like in the case of the above embodiment, and the elastic body 22 is 
pushed up by a magnet 24, in particular, deposition of the developer onto 
the developing roller 3 can be reduced effectively because of the multiple 
effect of blocking by the projected elastic body and of the reduced 
magnetic drawing by the magnet 24. 
The magnet 24 is placed under the developer feed section 20. By this 
arrangement, the developer is not pressed against the blade like in the 
case of conventional device where the developer is scraped off forcefully 
by a scrape blade. 
This effectively prevents blocking of toner in developer due to coagulation 
and also deterioration of carrier by breakage. This composition is also 
free from the trouble of developer splashed to the outside by swing motion 
of the blade when provided in the housing so as to swing freely. 
FIG. 6 and FIG. 7 show the 3rd embodiment of this invention, in which the 
magnet 24 is held by the guide member 23 so as to move up and down freely 
under the developer feed section 20 of the housing, and the cam 29 as a 
part of the developer feed control means is provided under the magnet 24 
so as to turn freely. 
The driving power of the gear 30 at the end of the cam 29 is turned on and 
off through the magnetic clutch 31 to turn the cam 29 as required, and the 
magnet 24 is moved up and down through the cam. 
In the above 2nd and 3rd embodiments, electrodes of the same polarity (N 
poles in the drawings) are provided at the developer feed section 20 of 
the developing roller 3 and at the top end of the magnet 24 facing to the 
section, and the magnetic drawing motion of the developing roller 3 is 
lowered effectively by the magnetic repulsion between the two poles while 
the roller is not used for development. 
If the magnetic force of the magnet 24 is far more greater than that of the 
magnetic roller 8 of the developing roller 3 and major portion of 
developer is drawn to the side of the magnet 24, however, the two poles 
may be of different polarity each other because the magnetic drawing force 
of the developing roller 3 is lowered as the result of the greater power 
of the magnet 24 and the effect of this invention can be attained. 
When the spacing between the bottom of the housing and the developing 
roller 3 is set smaller so that the magnetic force is fully applied to the 
developer feed section 20 when the magnet 24 comes close, there will be no 
need to raise the bottom by using the eastic body 22 for a part of the 
bottom plate. 
This invention is also applicable to the developing device of which 
developing roller 3 turns in the same direction as that of the 
photoreceptor drum 1. In this case, the developer feed section is formed 
over the developing roller 3, and the magnet 24 is positioned at the upper 
part of the housing, or the magnet 24 is positioned in the same manner as 
the above embodiments and the developing roller 3 is turned in reverse 
direction during the time of no development. 
FIG. 8 shows the developing of an electrostatic copying machine or others 
with two developing units 2a, 2b arranged vertically as the 4th of the 
present inventioned. The developing units 2a, 2b respectively comprise a 
housing containing developer of two components of toner and carrier, a 
developing roller 3 provided facing to the photoreceptor drum 1 on which 
electrostatic latent image is formed, a stirring roller 5 arranged in 
parallel to the developing roller 3, and a scraper 13 for toner scraping 
after development and provided over the stirring roller 5. 
The housing of each developing unit 2a, 2b contains developer of different 
color for multi-color development of the electrostatic latent image on the 
photoreceptor drum 1. 
The developing roller 3 is composed of a cylindrical rotary sleeve 7 turned 
in reverse direction to the photorecepter drum 1 by a driving means not 
illustrated, and a fixed type magnetic roller 8 provided in the rotary 
sleeve and having two or more N poles and S poles magnetically fixed on 
the periphery with certain spacing. 
By the magnetic force of the magnetic roller 8, developer is deposited onto 
the surface of the rotary sleeve 7 to form magnetic brush. The magnetic 
brush moves as the rotary sleeve 7 turns and is put in contact with the 
surface of the photoreceptor drum 1 at the opening 9 for development of 
the housing to develop the electrostatic latent image. A doctor blade 10 
to control the height of the magnetic brush is projected at the bottom of 
the housing. 
The toner kept in the toner hopper 11 at the upper part of the housing is 
supplied onto the stirring roller 5 through the feed roller 12 and is 
carried to the developing roller 3 while being mixed with the developer in 
the housing by the stirring roller 5. 
The developer carried by the stirring roller is deposited onto the surface 
of the rotary sleeve 7 to form magnetic brush at the position 
corresponding to the N pole made under the magnetic roller 8, i.e. at the 
developer feed section 20 positioned at the up-stream side of the doctor 
blade 10 turning in the direction of the developing roller 4. 
The bottom of the housing is notched in the range from the developer 
feeding section 20 to the lower part of the stirring roller, and the notch 
is covered with an elastic member 32 made of rubber or the like. 
A reinforcing plate 33 is provided under the elastic member 32, the bottom 
plate 34 made of the elastic member 32 and the reinforcing plate 33 is 
moved up and down by a driving means 35, and a hollow 36 is formed when 
the bottom plate 34 is lowered comprising a developer feed control means. 
As shown in FIG. 9, the driving means 35 is composed of a lever 38 held by 
a supporting shaft 37 to a side of the housing so as to turn freely, and a 
solenoid 39 as the driving source of the lever 38. One end of the lever 38 
is connected to the lower face of the reinforcing plate by a pin 40a, and 
the other end of the lever 36 is connected to the operating lever 41 of 
the solenoid 39 by a pin 40b. 
The operating lever 41 of the solenoid 39 is pushed in and out, which turns 
the lever 38 so that the bottom plate 34 is displaced between the 
condition where the elastic member 32 is expanded to lower the bottom 
plate 34 (See the developing unit 2b at lower part of FIG. 8) and the 
condition where the elastic member 32 is contracted to raise the bottom 
plate 34 of the housing (See the developing unit 2a at the upper part of 
FIG. 8). 
To operate a copying machine of the above composition, the bottom plate 34 
of the housing 2a of the unit containing the developer of the color used 
for developing is set at raised position, and the bottom plate 34 of the 
housing 2b of the other unit is set at lowered position. By this setting, 
the developer of the color not used for the development flows into the 
hollow 36 made when the bottom plate 34 of the housing goes down and is 
kept off the developer feed section 20 of the developing roller 3. 
Consequently, the developer drawing force of the developing roller 3 does 
not reach the developer and no magnetic brush is formed on the periphery 
of the developing roller, which prevents lowering of the print quality due 
to deposition of developer of the color not used for the development on 
the surface of the photoreceptor drum. 
The developer flew into the hollow 36 is not subjected to any compression 
as it is kept off the developing roller, which serves to effectively 
prevent blocking of the toner in the developer due to coagulation and also 
deterioration of the carrier by breaking. 
In addition, the developer is also free from such troubles as splashing to 
outside by the up-down motion of the bottom plate 34 because the up-down 
motion takes place at a position away from the opening 9 for development. 
In the above embodiment, a part of the bottom plate 34 is made of the 
elastic member 32 such as rubber and the bottom plate 34 is moved up and 
down by using elastic property of rubber material. It may also possible to 
provide a bellows at a part of the bottom plate in place of the rubber 
material and to use expansion and contraction of the bellows for up-down 
motion of the bottom plate. 
It may also possible to use a flexible material such as soft plastic for 
the bottom plate, to deform one end of the bottom plate in hinge form, and 
to hold the other end so as to slide freely along the side wall of the 
housing allowing the bottom plate to move up and down freely. 
The developing device of any one of the above embodiments of the invention 
is not limited to the type with fixed magnetic roller of the developing 
roller 3. The invention is also applicable to such developing devices 
where both the sleeve and the magnetic roller are rotary type or where the 
sleeve is stationary and the magnetic roller is rotary type.