Monocomponent developing device

A developing device adjoins a rotatably arranged photoreceptor, and is internally provided with a rotatably disposed developing roller confronting the photoreceptor. A cylindrically formed flexible film member having a peripheral length longer than that of the developing roller and loosely mounted thereover is included. A first member for forming a slack portion of the film member, for example, a regulating blade or a cleaning blade, and a second member for controlling the position of the slack portion of the film member, for example, a magnet is provided in the developing device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to a developing device for use in 
an electrophotographic copying machine, a printer or the like and more 
particularly, to a developing device which uses a monocomponent developer, 
and is capable of easily moving a developing means in and out of contact 
with a photoreceptor. 
2. Description of the prior Art 
Conventionally, Japanese Patent Laid-open Application No. 52-143831 
discloses one such monocomponent developing device, in which upon supply 
of the non-magnetic toner onto the surface of an elastic deveoping roller, 
a blade is pressed against the developing roller so that a thin layer of 
charged toner may be formed on the peripheral surface thereof and a toner 
image is, then, formed by bringing the thin layer of the charged toner 
into direct contact with the surface of the photoreceptor. 
Japanese patent Laid-open Application No. 55-77764 discloses another 
monocomponent developing device, in which an electrically conductive thin 
film is arranged on the surface of a developing roller consisting of an 
electrically conductive soft elastic foamed member. In this developing 
device, the toner is caused to adhere electrically to the surface of the 
developing roller with the use of a magnetic brush; and the toner is 
caused to adhere to an electrostatic latent image through contact between 
the developing roller and the surface of the photoreceptor to form the 
toner image. 
However, even in both of these methods, the formation of a thin layer of 
the charged toner necessitates keeping the blade in contact with the 
surface of the developing roller under a certain pressure greater than a 
perdetermined one. Therefore, the developing roller is required to be 
relatively high in hardness. On the contrary, to prevent the photoreceptor 
from being damaged or the image from being smeared on a contact portion 
between the developing roller and the photoreceptor, the developing roller 
is required to very softly contact the photoreceptor. But a developing 
roller which may satisfy both of these requisites cannot be obtained since 
these two requisites are completely opposed. Furthermore, in particular, 
in the case where a peripheral speed of the developing roller is to be 
differentiated from that of the photoreceptor, the image formed on the 
photoreceptor tends to be unclear. 
On the other hand, recently, the monocomponent developing devices with the 
above-mentioned method for developing through contact with the 
photoreceptor are used for the development of exchanging the color of an 
image. In this development, when two developing devices simultaneously 
contact with a photoreceptor, there arises the problem that the developer 
of one developing device intrudes into the developer of another developing 
device. 
For resolving this problem, Japanese Patent Laid-open application No. 
62-15574 and No. 62-15575 conventionally disclose methods, in which only 
the necessary developing device for development is caused to contact with 
a photoreceptor following the displacement of another unnecessary 
developing device. 
Meanwhile, even in the case of a single color development using a single 
developing device, the developing device must be taken out in a direction 
of the axis of a photoreceptor for the purpose of exchanging the 
developing device to change the color of an image and the maintenance of 
an apparatus. For this reason, a developing device is required to be moved 
away from the photoreceptor in order to release the contact between a 
developing roller and a photoreceptor. 
However, in order to release the contact between a photoreceptor and a 
developing roller in conventional developing devices, the whole developing 
device was required to be moved away from the photoreceptor. There arises 
the problem that the construction of an apparatus of this type become 
quite complicated. 
SUMMARY OF THE INVENTION 
The main object of the present invention is to provide a monocomponent 
developing device, in which the contact or the non-contact between a 
developing roller and a photoreceptor can be controlled without moving the 
whole device. 
Another object of the present invention is to provide a monocomponent 
developing device, which facilitates the exchange of a developing device 
without causing mixing of colors of toners for making multi-colored 
development. 
Still another object of the present invention is to provide a monocomponent 
developing devide, which facilitates the exchange of the toner color and 
the maintenance of an apparatus which makes single-colored development. 
These and other objects of the present invention can be achieved by 
providing a monocomponent developing device, which comprises a rotatably 
disposed developing roller confronting a photorecepter, a cylindrically 
formed flexible film member having a peripheral length longer than that of 
the developing roller and loosely mounted thereover, and positioning means 
to position the flexible film member partly into and out of contact with 
said photoreceptor, said positioning means including means to form a first 
slack of the flexible film member at a location confronting said 
photoreceptor for the flexible film member to contact with the 
photoreceptor while the remaining portion of the flexible film member is 
in contact with the developing roller and to form a second slack of the 
flexible film member at a location remote from the location confronting 
said photoreceptor for the flexible member to be out of contact with the 
photoreceptor. 
These and other objects, advantages and features of the invention will 
become appararent from the following description thereof taken in 
conjunction with the accompanying drawings which illustrate a specific 
embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a cross-sectional view of a developing device 1 according to a 
first embodiment of the present invention. The developing device 1 adjoins 
a photoreceptor drum 100 rotatably driven in a direction as shown by an 
arrow (a). The developing device 1 comprises a rotatably arranged 
developing roller 3, a film member 2 consisting of a cylindrical 
electroformed nickel film (the film thickness : 40 .mu.m) which is loosely 
mounted around the developing roller 3, a substantially semicircular 
magnet 4 arranged inside of said developing roller 3, a regulating blade 5 
pressing against the external surface of said film member 2 for charging a 
toner and preventing the film member slacking, a cleaning blade 6 for 
levelling off a residual toner after developing at the down stream side 
from a region where the development is carried out with respect to the 
direction of the rotation of the developing roller, and a casing 7 
accomodating these components as well as toners. A toner storing 
compartment 8 is provided into the casing 7. Said toner storing 
compartment 8 has agitators 9 and 10 rospectively rotating in a direction 
as shown by an arrow (c) in order to transport the toner to a direction as 
shown by the arrow (c) while preventing the toner from solidifying. 
By use of the semicircular magnet 4, the regulating blade 5, and the 
cleaning blade 6, the film member 2 is attracted to the developing roller 
3 at the opposite side to the side confronting the photoreceptor drum 100. 
More specifically, a slack section of the film member is formed on the 
side confronting the photoreceptor by attraction of the magnet and 
frictional force exerted between the regulating blade 5 or the cleaning 
blade 6 and the film member rotating with the developing roller, and this 
slack of the film member is caused to contact with the photoreceptor by 
the magnet, the regulating blade and the cleaning blade. 
It is to be noted here that the film member 2, the developing roller 3, and 
the regulating blade 5 and the cleaning blade 6 are selected to satisfy 
the relationship of .mu..sub.1 &gt;.mu..sub.2, wherein the coefficient of the 
friction between the external surface of the developing roller 3 and the 
internal surface of the film member 2 is .mu..sub.1, and that between the 
external surface of the film member 2 and the blade 5 or the cleaning 
blade 6 is .mu..sub.2. Conseguently, with the rotation of the developing 
roller 3 in a direction as shown by the arrow (b), the film member 2 is 
moved in the same direction. 
The external surface of a magnet 4 has the semicircular shape in order to 
fit into the internal surface of the developing roller 3. Said 
semicircular magnet 4 has a plurality of poles at the external surface 
thereof. When the developing device is out of operation, this semicircular 
magnet 4 occupies the position as shown in FIG. 1 (b) in which the magnet 
occupies the position confronting the photoreceptor. While the developing 
device is in operation, the semiconductor magnet 4 rotates for a half 
rotation by a driving source (shown in FIGS. 2 (a) and (b)) to occupy the 
position as shown in FIG. 1 (a) in which the magnet 4 occupies the 
position opposite to the position confronting the photoreceptor. 
The mechanism of said driving source will be explained with reference to 
FIGS. 2 (a) and (b). 
As shown in FIG. 2 (a), one end 4a of a shaft of the magnet 4 is supported 
by a bearing 3C provided within the developing roller 3 and another end 4b 
of the shaft of the magnet 4 is supported by one side wall of the casing 
7. The magnet 4 rotates at a predetermined angle by a moving means 40 
mentioned hereinbelow. 
Meanwhile, the developing roller 3 has a bearing 3b on the right side in 
FIG. 2 (a) which is supported by the shaft 4b of the magent 4 and another 
support shaft 3a on the opposite side which is supported by another side 
wall of the casing 7. The developing roller 3 rotated by a driving means 
30. 
Agitators 9 and 10 have shafts 9a and 10a respectively supported by side 
walls of the casing 7 for being rotatably driven by the driving means 30. 
As shown in FIG. 2 (a), a belt 31 is bridged over on both of the shaft 3a 
of the developing roller 3 and the shaft 9a of the agitator 9. Similarly a 
belt 32 is also bridged over on both of the shaft 9a of the agitator 9 and 
the shaft 10a of the agitator 10. 
Moreover, arranged at the end of the shaft 9a of the agitator 9 is a gear 
33 which is engaged with a driving gear 35 of a motor 34. 
Accordingly in the case where the driving gear 35 is caused to rotate in a 
direction as shown by an arrow (d) in FIG. 2 (a), the gear 33 and the belt 
31 and 32 respectively move in directions as shown by the arrows f, h and 
i and at the same time the developing roller 3 and the agitators 9 and 10 
rotate respectively in directions as shown by the arrows (b) and (c). 
The moving means 40 of the magnet 4 mentioned above, is composed of a 
sprocket 41, a chain 42, a spring 43 and a solenoid 44 as shown in FIG. 2 
(b). The sprocket 41 is fixed at the end of the shaft 4b of the magnet 4. 
One end of the spring 43 fixed in the casing 7 is attached to one end of 
the chain 42 for consistently urging the chain 42 in a direction as shown 
by an arrow (e). Further, a plunger 45 of the solenoid 44 is attached to 
another end of the chain 42 so as to allow the magnet 4 to rotate by the 
energization of the solenoid 44 in a direction as shown by an arrow (e') 
against the urging force of the spring 43. 
When the solenoid 44 is in operation, the magnet 4 rotates for a half 
rotation in the direction as shown by the arrow (e') to occupy the 
position as shown in FIG. 1 (b) in which the magnet occupies the position 
confronting the photoreceptor. 
On the contrary, when the solenoid 44 is out of operation, the magnet 4 
rotates for a half rotation in the direction as shown by the arrow (e) to 
occupy the position as shown in FIG. 1 (a). 
Comparing the case where the magnet 4 is moved following the stop of the 
rotation of the developing roller 3 with the case where the magnet 4 is 
moved using the rotative force of the developing roller 3, the latter case 
would be preferred because the slack of the film member is more smoothly 
formed and the movement of the magnet is more smoothly achieved. 
Furthermore, the cleaning blade 6 is provided in pressing the film member 
so as not to affect the slack portion of the film member. 
The developing roller is made of electrically conductive materials such as 
aluminium, in which the surface is made rough by a blast treatment, rubber 
or plastic materials in which electrical conductivity is provided by 
carbon or the like. A developing bias voltage is applied to the developing 
roller. 
The film member has a peripheral length somewhat longer than that of the 
developing roller so as to be loosely mounted thereover for forming a 
small portion of the film slack. Materials capable of being attracted by 
the magnetic force can be used to form the film member. Examples of such 
materials are a film having a thickness of about 30 to 200 .mu.m wherein 
metallic fine particles or the like are added to the soft resins such as 
polycarbonate, nylon, Teflon (trademark) or the like, a metallic thin film 
of nickel, stainless steel or the like having a thickness of 30 to 50 
.mu.m, or a laminated film of the aforementioned resinous film and 
metallic thin film. 
Materials having elasticity are the preferably used for forming the 
regulating blade 5. Examples of such materials are a magnetic and metallic 
thin plate, or a non-magnetic and metallic thin plate such as stainless 
steel, phosphor bronze or the like, a plastic plate of Teflon (trademark), 
nylon, or the like, an elastic plate of Teflon (trademark) rubber, 
silicone rubber or the like, and a laminated plate of the above-mentioned 
plastic plates. In short, materials conventionally used for forming a 
toner layer regulating blade can be used for forming the regulating blade 
5. The materials which are remote from the toner in triboelectric series 
are desirable for forming the regulating blade 5. In the case where 
positive toner is used as a developer, materials which are suitable for 
forming the regulating blade are a resinous plate of fluorine resin; 
Teflon (trademark), or the plate coated by the fluorine resin. While in 
the case where negative toner is used as a developer, materials which are 
suitable for forming the regulating blade are a resinous plate of 
polyamide film; nylon, or the plate coated by the polyamide resin. 
It is to be noted here that although monocomponent non-magnetic toner is 
preferably used in the developing device of this embodiment, magnetic 
toner may be used therein. 
The operation of the developing device 1 of the first embodiment in the 
present invention during the development will be explained hereinafter. 
In FIG. 1 (a), To shows the toner accommodated within the toner storing 
compartment 8, X shows a developing region where the film member 2 
contacts with the photoreceptor, and S shows a space formed between the 
developing roller 3 and the film member 2. 
On condition that the developing roller 3 and the agitators 9 and 10 are 
caused to rotate by the driving means 30 respectively in directions as 
shown by the arrows (b) and (c), the toner To accommodated within the 
toner storing sompartment 8 is forcibly moved in the direction shown by 
the arrow (c) under an effect of stirring by the agitators 9 and 10. 
Meanwhile, the film member 2 is driven to rotate in a direction as shown by 
the arrow (b) under the influence of frictional force exerted between it 
and the developing roller 3. The toner To accommodated within the toner 
storing compartment 8, which is in contact with the film member 2, is 
caused to adhere to the surface of the film member 2 by the action of 
electrostatic force so as to be transported in the direction as shown by 
the arrow (b). The toner To is held on the surface of the film member 2, 
and when it reaches the portion pressed by the regulating blade 5 on the 
surface of the developing roller 3, the toner To is applied uniformly in 
the form of a thin layer to the surface of the film member 2 and given a 
predetermined positive or negative polarity through the friction 
therewith. 
When the toner To held on the surface of the film member 2 under the 
influence of its own electrostatic force, it is delivered to a developing 
region X confronting the photoreceptor drum 100, the toner To is caused to 
adhere to an electrostatic latent image formed on the surface of the 
photoreceptor drum 100 to form a toner image in accordance with a voltage 
difference between a surface voltage of the photoreceptor drum 100 and the 
bias voltage applied to the developing roller 3. 
Since the film member 2 in contact with the photoreceptor drum 100 is never 
brought into contact with the developing roller due to the existence of a 
space S, the film member 2 softly and uniformly contacts with the 
photoreceptor drum 100 through its suitable nip width so that the latent 
image formed on the photoreceptor drum 100 may be turned to the uniform 
toner image. It is to be noted here that a peripheral speed of the 
photoreceptor drum 100 can be caused to differ from that of the film 
member 2, resulting in that the toner image once formed on the 
photoreceptor drum 100 can never be broken by physical force such as a 
rubbing force or the like. In particular, in the case where the peripheral 
speed of the film member 2 is set faster than that of the photoreceptor 
drum 100, the density of an image can be increased so that fogging can be 
effectively prevented in a non-image portion. 
The toner To having passed the developing region X is successively 
transported, together with the film member 2, in a direction as shown by 
the arrow (b). When the toner To passes between the cleaning blade 6 and 
the film member 2, an image pattern from which the toner To has already 
been consumed in the developing region X is erased so that the uniformity 
of the toner layer may be obtained. 
Subsequently, the toner To is supplied again to the surface of the film 
member 2 by the rotation of agitator 9 and 10, and then, the thin layer of 
the charged toner is uniformly formed again on the surface of the film 
member 2 at the pressure portion of the regulating blade 5, and the 
aforementioned operation is repeated thereafter. 
Meanwhile when the developing device is out of operation, the magnet 4 
rotates for a half rotation in order to absorb the film member 2 to the 
developing roller 3 at the side confronting the photoreceptor. As a 
result, the slack portion of the film member 2 is formed at the side 
opposite to the side confronting the photoreceptor; 
FIG. 3 (a) which is a cross-sectional view of a developing device as 
another example of the first embodiment of the present invention shows the 
condition during the development. In the developing device shown in FIG. 3 
(a), a bar shaped magnet 4 with only one N-S pole within the developing 
roller 3 faces against the regulating blade 5. Accordingly by use of the 
regulating blade 5, the cleaning blade 6, and the magnet 4, the film 
member is attracted to the developing roller 3. It is to be noted here 
that the developing roller, the film member, the cleaning blade and the 
regulating blade are selected to satisfy the relationship of .mu..sub.1 
&gt;.mu..sub.2 &gt;.mu..sub.3, wherein the coefficient of the friction between 
the external surface of the developing roller and the internal surface of 
the film member is .mu..sub.1, that between the cleaning blade and the 
external surface of the film member is .mu..sub.2, and that between the 
regulating blade and the external surface of the film member is 
.mu..sub.3. When a thin layer of toner is formed on the surface of the 
film member, the coefficient of the friction between the regulating blade 
and the external surface of the film member changes as well as that 
between the cleaning blade and the external surface of the film member. 
However, the relationship among the above-mentioned .mu..sub.1, 
.mu..sub.2, and .mu..sub.3 remains unchanged. The magnet 4 located below 
the regulating blade improves the adhesivity between the film member and, 
the developing roller so as to prevent the film member from forming a 
slack portion before passing under the regulating blade. As a result, the 
film member can always move in a stable condition. 
FIG. 3 (b) shows the developing device of FIG. 3 (a) in non-contacting 
condition. The magnet 4 rotates at an angle of 90.degree. in synchronism 
with the rotation of the developing roller in order to face the 
photoreceptor. Therefore, the slack of the film member which is in contact 
with the photoreceptor is absorbed and adhered to the surface of the 
developing roller in order to release the contact between the 
photoreceptor and the developing roller, and then, the slack is formed 
downstream from the developing region X with respect to the direction of 
the rotation of the developing roller. 
FIG. 4 (a) is a cross-sectional view of a developing device as still 
another example of the first embodiment of the present invention. In FIG. 
4 (a), a magnet is an electromagnet 12 confronting a photoreceptor. The 
film member is caused to adhere by the regulating blade 5 and the cleaning 
blade 6. It is to be noted here that the developing roller, the cleaning 
blade, the film member, the regulating blade are selected to satisfy the 
relationship of .mu..sub.1 &gt;.mu..sub.2 &gt;.mu..sub.3, wherein the 
coefficient of the friction between the external surface of the developing 
roller and the internal surface of the film member is .mu..sub.1, that 
between the cleaning blade and the external surface of the film member is 
.mu..sub.2, and that between the regulating blade and the external surface 
of the film member is .mu..sub.3. The electromagnet 12 is kept deenergized 
during the development as shown in FIG. 4(a). As a result, the space S is 
formed between the film member 2 and the developing roller 3 at the side 
confronting the photoreceptor to maintain the contact between the 
photoreceptor and the filmy member. 
While, in the case of the non-development, the electromagnet 12 is 
electrically energized in order to be able to operate. Therefore, as shown 
in FIG. 4(b), the electromagnet 12 absorbs the film member 2 to the 
developing roller at the side confronting the photoreceptor in order to 
release the contact between the film member 2 and photoreceptor 100, 
resulting in that the slack of the film member 2 is formed at the side 
opposed to the side confronting the photoreceptor. 
FIG. 5 is a cross-sectional view of two developing devices of the first 
embodiment of the present invention disposed around the photoreceptor. In 
a first developing device 21, the magnet 4 faces to the side confronting 
the photoreceptor so as to absorb the film member 2 to the developing 
roller 3 by its own attraction, so that the film member 2 releases the 
contact with the photoreceptor 100. On the other hand, in a second 
developing device 22, the magnet 4 faces to the opposite side to the side 
confronting the photoreceptor so as to absorb the film member 2 to the 
developing roller 3 by its own attraction. As a result, the slack of the 
film member 2 is formed at the side confronting the photoreceptor of the 
developing roller in order to bring the film member 2 into contact with 
the photoreceptor 100, and the development by the developing device 23 is 
carried out. 
FIG. 6 (a) is a cross-sectional view of a developing device 1 embodying a 
second embodiment of the present invention. A roller 50 regulating the 
thin layer of the toner (hereinafter referred to as a regulating roller 
50) is arranged in pressing contact with the developing roller. The 
regulating roller presses the film member 2 in order to regulate the 
rotation of the film member and to charge the toner. The cleaning blade is 
in pressing contact with the film member 2 as well as the regulating 
roller 50. 
Further, a toner storing compartment 8 accommodates a toner supply blade 9 
and an agitator 10 rotating in a direction as shown by the arrow (d). The 
toner To accommodated within the toner storing compartment 8 is 
transported forwards while being prevented from solidifying by the toner 
supply blade and the agitator. Except for the above-mentioned items, the 
developing device 1 is similar in construction to the one of the first 
embodiment. 
The regulating roller 50 rotates in a direction opposite to the direction 
as shown by the arrow (b) to transport the film member 2 toward the side 
confronting the photoreceptor 100. Meanwhile the cleaning blade 6 presses 
contact with the film member 2, so that the slack of the film member 2 is 
formed at the developing region X. As a result, the film member 2 contacts 
with the surface of the photoreceptor. 
It is to be noted here that the developing roller 3, the film member 2, the 
regulating roller 50, and the cleaning blade 6 are selected to satisfy the 
relationship of .mu..sub.1 &gt;.mu..sub.2, wherein the coefficient of 
friction between the external surface of the doveloping roller 3 and the 
internal surface of the film member 2 is .mu..sub.1, that between the 
external surface of the film member 2 and the regulating roller 50 or the 
cleaning blade 6 is .mu..sub.2. Therefore, the film member 2 moves in the 
direction as shown by the arrow (b) with the rotation of the developing 
roller 3. 
The regulating roller 50 consists of an elastic rubber roller, or a roller 
provided with a laminated layers which includes a resin layer as the upper 
layer, a foamed urethane layer as the middle layer, and an elastic rubber 
layer as the lower layer. To effectively give a predetemined polarity to 
the toner, materials which remote from the toner in the triboelectric 
series should be selected for forming the surface of the regulating roller 
50. Further, in the case where the developing roller 3 has elasticity, a 
metallic roller of aluminum or the like can be used as the regulating 
roller 50. 
When the developing device 1 is in operation, the regulating roller 50 
rotates in a direction opposite to the direction as shown by the arrow (b) 
as shown in FIG. 6 (a). On the contrary, when the developing device is out 
of operation, the regulating roller 50 rotates in the same direction as 
the developing roller 3 for a predetermined time in order to form the 
slack of the film member 2 at the side opposite to the side confronting 
the photoreceptor. In another way, the regulating roller 50 stops rotating 
in order to form the slack of the film member 2 at the side opposite to 
the side confronting the photoreceptor. 
It is to be noted here that the developing roller of the second embodiment 
in the present invention is similar in materials to the one of the first 
embodiment. 
Examples of materials used for the film member are soft resinous sheet, for 
example, polycarbonate, nylon, Teflon (trademark) or the like, a sheet of 
such resin including carbon or metallic fine particles or the like having 
a thickness 30 to 200 .mu.m, a metallic thin film of nickel, stainless 
steel, aluminun or the like having a thickness of 30 to 50 .mu.m, or a 
laminated sheet of the aforementioned resionous sheet and metallic thin 
film. In particular, in case of using a usinous sheet of these sheets and 
films, the resinous sheet remote from the toner in triboelectric series 
should be used. 
When positive toner is used as a developer, materials which are suitable 
for forming the film member are fluoride resin; 
ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene 
(PTFE) or the like. Meanwhile when negative toner is used as a developer, 
materials which are suitable for forming the film member are polyamide 
resin; nylon or the like. 
It is to be noted here that both of magnetic and non-magnetic toners can be 
used as monocomponent toner in the developing device of this embodiment. 
The operation of the developing device of this embodiment will be explained 
hereinafter. 
During the development, as shown in FIG. 6 (a), on condition that the 
developing roller 3, the toner supply blade 9 and the agitator 10 are 
caused to rotate by the driving means 30 shown in FIG. 2 (a) respectively 
in directions as shown by the arrows (b) and (d), the toner To 
accommodated within the toner storing compartment 8 is forcibly moved in 
the direction shown by the arrow (d) under an effect of stirring by the 
toner supply blade 9 and the agitator 10. 
Meanwhile, the film member 2 is driven to rotate in the direction as shown 
by the arrow (b) under the influence of frictional force exerted between 
it and the developing roller 3. 
The toner To accommodated within the toner storing compartment 8, which is 
in contact with the film member 2, is caused to adhere to the surface of 
the film member 2 by the action of electrostatic force to be transported 
in the direction as shown by the arrow (b). And then, the toner To, held 
on the surface of the film member 2; reaches the portion pressed by the 
regulating roller 50 on the surface of the developing roller 3. The 
regulating roller 50 rotates while contacting with the developing roller 3 
in a direction opposite to the direction as shown by the arrow (b) with a 
faster or slower speed than the film member 2 driven by the developing 
roller 3, so that the toner To is applied uniformly in the form of a thin 
layer on the surface of the film member 2 and is changed through the 
friction therewith. 
The toner To held on the surface of the film member 2 under the influence 
of its own electrostatic force, forms a toner image to be developed 
through the a process similar to the first embodiment. 
Since the film member 2 in contact with the photoreceptor drum 100 is never 
brought into contact with the developing roller due to the existence of 
the space S, the film member 2 softly and uniformly contacts with the 
photoreceptor drum 100 through its suitable nip width so that the latent 
image formed on the photoreceptor drum 100 may be turned to the uniform 
toner image. 
It is to be noted here that a peripheral speed of the photoreceptor drum 
100 can be caused to differ from that of the film member 2, resulting in 
that the toner image once formed on the photoreceptor drum 100 can never 
be broken by physical force such as rubbing force or the like. In 
particular, in the case where the peripheral speed of the film member 2 is 
set faster than that of the photoreceptor drum 100, the density of an 
image can be increased, so that a fogging can be effectively prevented in 
a non-image portion. 
The toner To having passed the developing region X is successively 
transported, together with the film member 2 in a direction as shown by 
the arrow (b). When the toner To passes between the cleaning blade 6 and 
the film member 2, an image pattern from which the toner To has already 
been consumed in the developing region X is erased so that the uniformity 
of the the toner layer may be obtained. 
Subsequently, the toner is supplied again to the surface of the film member 
2 by the rotation of the toner supply blade 9, the thin layer of the 
charged toner is uniformly formed again on the surface of the film member 
2 at the pressure portion of the regulating roller 50, and the 
aforementioned operation is repeated thereafter. 
On the other hand, when the developing device 1 does not operate, as shown 
in FIG. 6 (b), a clutch of the driving system (not shown) for the 
regulating roller 50 is switched so as to rotate the regulating roller 50 
in the direction as shown by the arrow (b). In another way, the rotation 
of the regulating roller 50 is caused to stop, moreover, the developing 
roller is deenergized after a predetermined time has passed. 
By either of these two ways to rewind the film member 2, the slack of the 
film member 2 can be formed at the opposite side to the developing region 
X of the developing roller in order to release the contact between the 
photoreceptor 100 and the film member 2. 
FIG. 7 is a cross-sectional view of a developing device as another example 
of the second embodiment of the present invention. In the developing 
device as shown in FIG. 7 (a), a pressing roller 14, the regulating blade 
5, and the cleaning blade 6 respectively are in pressing contact with the 
film member 2. Therefore, as shown in FIGS. 7(b) and (c), when the 
developing device stops its developing operation, the pressing roller 14 
rotates in the direction as shown by the arrow (b) by switching a clutch 
15 as in the case of the above-mentioned FIG. 6 to form the slack of the 
film member at the opposite side to the side confronting the 
photoreceptor, so that the film member 2 releases the contact with the 
photoreceptor. 
As another example of the second embodiment, the developing operation may 
be discontinued by terminating the rotation of the pressing roller 14 by 
engaging a stopper 16 with a clutch gear 18 through the activation of a 
solenoid 17 as shown in FIG. 7 (d). It is to be noted here that the 
stopper 16 is pulled up by a spring 15 in order not to contact with said 
clutch gear 18 during the development. Furthermore, the film member 2, the 
developing roller 3, the cleaning blade 6, the regulating blade 5, and the 
pressing roller 14 are selected to satisfy the relationship of .mu..sub.1 
&gt;.mu..sub.4 &gt;.mu..sub.2 &gt;.mu..sub.3, wherein the coefficient of the 
friction between internal surface of the film member 2 and the external 
surface of the developing roller 3 is .mu..sub.1, that between the 
external surface of the film member 2 and the cleaning blade 6 or the 
regulating blade 5 or the pressing roller 14 being at a standstill are 
respectively .mu..sub.2, .mu..sub.3, and .mu..sub.4. Consequently, when 
the pressing roller 14 stops, the slack of the film member moves from the 
side confronting photoreceptor to the opposite side in synchronism with 
the rotation of the developing roller 3, so that the contact between the 
film member and the photoreceptor is released as shown in FIG. 7 (b). 
FIG. 8 (a) is a cross-sectional view of a developing roller as still 
another example of the second embodiment of the present invention. In FIG. 
8 (a), a pressing roller 24 is arranged at the downstream side from the 
developing region X with respect to the direction of the rotation of the 
developing roller 3 so as to press having a pressing contact with the film 
member 2. Similarly a regulating blade 25 having a pressing contact with 
the film member 2. Therefore, as shown in FIG. 8 (a), during the 
development, the pressing roller 24 is caused to stop its own rotation by 
the a stopper (not shown) similar to the one shown in the above-mentioned 
FIG. 1 (d). The pressing roller 24 at rest rubs the film member 2 to form 
the slack of the film member 2 at the side confronting the photoreceptor, 
resulting in the space S being formed between the film member 2 and the 
developing roller 3 so as to keep contact between the film member 2 and 
the photoreceptor. 
During the undevelopment, the pressing roller 24 rotates freely to form the 
slack of the film member at the side opposite to the side confronting the 
photoreceptor as shown in FIG. 8 (b), so that the contact between the 
photoreceptor 100 and the film member is released. 
It is to be noted here that the regulating blade 25 is similar in materials 
to the regulating blade 5 arranged in the developing device of the first 
embodiment. 
FIG. 9 is a cross-sectional view of two developing devices of the second 
embodiment according to the present invention disposed around the 
photoreceptor. In FIG. 9, when a developing device 51 is at rest, a 
regulating roller 54 stops following its rotation in the direction as 
shown by the arrow (b). As a result, the slack of the film member is 
formed at the opposite side to the developing region X so as to prevent 
the film member 2 from contacting with the photoreceptor 100. On the other 
hand, when a second developing device 53 is in operation, the regulating 
roller 54 rotates in the direction opposite to the direction as shown by 
the arrow (b). Subsequently, the pressure to the film member 2 by the 
regulating roller 54 and the cleaning blade 56 forms the slack of the film 
member 2 at the side confronting the photoreceptor of the developing 
roller 3 in order to bring the film member 2 into contact with the 
photoreceptor. As a result, the developing operation is performed. 
FIGS. 10 (a) and (b) are cross-sectional views of a developing device of a 
third embodiment of the present invention, FIG. 11 (a) is a perspective 
view showing the position of guide members in said developing device 
during the development. FIG. 11 (b) is a side view of said guide members 
during the development. The developing device of the third embodiment is 
similar in construction to the one of the second embodiment, except for 
the developing roller. Each end of the developing roller 3 is provided 
with a guide member 60 which can rotate having its own axis jointly with 
said developing roller 3. 
The guide members 60 consist of pressing portions 60a for pressing 
substantially half periphery of the film member 2 arranged around the 
developing roller and support plates 60b for supporting said pressing 
portions so as to turn round on the axis of the developing roller. The 
internal shape of the pressing portions 60a in the guide members 60 fits 
the external shape of the developing roller. It is to be noted here that 
the internal shape of the pressing portions 60a necessitates substantially 
fitting the external shape of the developing roller. Consequently, the 
shape of the pressing portions is not restricted to the one as shown in 
FIG. 11 (a). 
Moreover, the internal shape of the pressing portions 60a necessitates 
sticking elastic compound sheets of foamed polyurethane sheets and 
polyester sheets or the like for the purpose of causing to the film member 
adhere to the developing roller. Further, the internal shape of the 
pressing portions 60a may be a tape of fluorine, for example, Teflon 
(trade mark) or the like so that the film member can smoothly slip at the 
portion where the guide members 60 adheres to the film member. 
As shown in FIG. 13, the outside of each of said guide members 60 is 
provided with a side plate 61 which can turn round on the axis of the 
developing roller 3. Each of the side plates 61 has two concavities which 
are parallel to the axis of the developing roller 3; 6a and 6b as well as 
two pins 7a and 7b as a stopper for piercing the side plate 61 through the 
two concavities. The pins 7a and 7b are urged outward (in the left 
direction in FIG. 13) by springs accommodated within the above-mentioned 
concavities; 6a and 6b. 
The outside of each side plate 61 is provided with a cam plate 64 which can 
turn round on the axis of the developing roller, so that the movement of 
the pins 7a, 7b is controlled by them. In other words, as shown in FIG. 
14, the inside of said cam plate 64 (the side confronting the developing 
roller) consists of a convex cam surface 10a pushing the pin 7a or 7b 
toward the guide member 60 using the spring 8a or 8b and a concave cam 
surface 10b retrieving the pin 7a or 7b using the spring 8a or 8b. 
Further, the inside of said cam plate 64 contacts with the end of the 
support plate 60b of the guide member through the pins for the purpose the 
rotation of the guide member 60. At the outside of each of cam plate 64, a 
clutch 62 and an electromagnetic coil 63 which absorbs and drives said 
clutch plate 62 are disposed around the axis of the developing roller. 
Said electromagnetic coil absorbs the clutch plate 62, so that the cam 
plate 61 rotates. 
In a casing 7, a toner storing compartment 8 is arranged. Arranged in said 
toner storing compartment 8 are the toner supply blade 9 and the agitator 
10 which respectively rotate in the direction as shown by the arrow (d) in 
order to transport the toner while preventing the accommodated toner To 
from solidifying. 
As shown in FIG. 11 (a), the film member 2 is caused to adhere around the 
developing roller 3 by the pressing portion 60a, resulting in that the 
slack portion of the film member 2 concentrates at an opening portion of 
the guide member provided at the side confronting the photoreceptor drum 
so as to form the space S. Through this process, the film member 2 
contacts the photoreceptor 100. 
It is to be noted here that the developing roller 3, the film member 2, and 
the regulating blade 5 or the cleaning blade 6 are selected to satisfy the 
relationship of .mu..sub.1 &gt;.mu..sub.2, wherein the coefficient of the 
friction between the external surface of the developing roller 3 and the 
internal surface of the film member 2 is .mu..sub.1, that between the 
external surface of the film member 2 and the regulating blade 5 or the 
cleaning blade 6 is .mu..sub.2. Accordingly, in synchronism with the 
rotation of the developing roller 3 in the direction as shown by the arrow 
(b), the film member 2 also rotates in the same direction. 
The developing roller, the film member, the regulating blade and the toner 
used in the developing device of the third embodiment are similar in 
materials to the ones used in the developing device of the first 
embodiment. 
The operation of the developing device 1 having the above described 
construction will be explained hereinafter. 
During the development, as shown in FIG. 10 (a), FIG. 11 (a) and (b), on 
condition that the upper pin 7a; pushing toward the developing roller 
fixes the end of the support plate 60b of the guide member 60 trying to 
rotate with the developing roller 3 in the direction as shown by the arrow 
(b), the operation is carried out. Therefore, as shown in FIG. 10 (a), the 
developing roller 3, the supply blade 9, and the agitator 10 are caused to 
rotate by a driving means 30 respectively in directions as shown the 
arrows (b) and (d), resulting in that the toner To accommodated within the 
toner storing compartment 8 is forcibly moved in a direction shown by the 
arrow (d) under an effect of stirring by the supply blade 9 and the 
agitator 10. 
Meanwhile, the film member 2 is driven to rotate in the direction as shown 
by the arrow (b) under the influence of frictional force experted between 
it and the developing roller 3. 
The toner To accommodated within the toner storing compartment 8, which is 
in contact with the film member 2, is caused to adhere to the surface of 
the film member 2 by the action of electrostatic force, and then, is 
transported in the direction as shown by the arrow (b). When the toner To 
held on the surface of the film member 2 reaches the portion pressed by 
the regulating blade 5 on the surface of the developing roller 3, the 
toner To is applied uniformly in the form of a thin layer on the surface 
of the film member 2 and charged through the friction therewith. 
The thin layer of the toner is held on the surface of the film member 2 
under the influence of its own electrostatic force, which forms a toner 
image to be developed through the similar process similar to that of the 
first embodiment. 
Since the film member 2 in contact with the photoreceptor drum 100 is never 
brought into contact with the developing roller due to the existence of 
the space S, the film member 2 softly and uniformly contacts with the 
photoreceptor drum 100 through its suitable nip width so that the latent 
image formed on the photoreceptor drum 100 may be turned to the uniform 
toner image. In the case where a peripheral speed of the photreceptor drum 
100 is caused to differ from that of the film member 2, the toner image 
once formed on the photoreceptor drum 100 can never be broken by physical 
force such as a rubbing force or the like. In particular, in the case 
where the peripheral speed of the film member 2 is set faster than that of 
the photoreceptor drum 100, the density of an image can be increased, so 
that a fogging can be effectively prevented in a non-image portion. 
The toner To having passed the developing region X is successively 
transported, together with the film member 2, in the direction as shown by 
the arrow (b). When the toner To passes between the cleaning blade 6 and 
the film member 2, an image pattern from which the toner To has already 
been consumed in the developing region X is erased so that the uniformity 
of the toner layer may be obtained. 
Subsequently, the toner is supplied again on the surface of the film member 
2 by the rotation of the toner supply 9, and then the aforementioned 
operation is repeated thereafter. 
On the other hand, in the case where the development by the developing 
device 1 is not carried out, as shown in FIG. 10(b) and FIGS. 12 (a) and 
(b), the upper pin 7a is retracted by the rotation of the above-mentioned 
cam plate 64, and at the same time, the lower pin 7b advances toward the 
developing roller. Moreover, after a predetermined time has passed, the 
driving of the developing roller is stopped. As a result, the guide member 
rotates for substantially half rotation in order to be located at the side 
confronting the photoreceptor 100, so that the slack portion of the film 
member 2 is formed at the opposite side of the developing roller to the 
side confronting the photoreceptor. Through this process, the contact 
between the film member 2 and the photoreceptor 100 is released. 
FIG. 15 is a cross-sectional view of two developing devices of the third 
embodiment disposed around the photoreceptor. In FIG. 15, when the 
developing device 65 is at rest, the upper pins are retracted, and at the 
same time, the lower pins 7b advances. Therefore each of the guide members 
is located at the side controlling the photoreceptor in order to release 
the contact between the film member 2 and the photoreceptor 100. 
Meanwhile, when a second developing device 66 is in operation, the upper 
pin 7a advances and the lower pin 7b is retracted. As a result, the guide 
member 60 is fixed at the position opposite to the first developing device 
65 in order to form the slack portion of the film member 2 at the side 
confronting the photoreceptor of the developing roller. Subsequently, the 
film member 2 contacts with the photoreceptor 100 to carry out the 
development. 
FIG. 16 is a cross-sectional view of a developing device 1 of a fourth 
embodiment according to the present invention. FIG. 17 (a) and FIG. 18 (a) 
are perspecting views showing the main parts of the developing device 1. 
The developing device 1 is generally similar to the one of the third 
embodiment. 
The outside of each guide member 60 is provided with a side plate 71 (shown 
in FIG. 18 (a)). Each of side plates 71 has a pin 70 which is a stopper 
projecting parallel with the axis of the developing roller 3. The pin 70 
is in contact with the end of the support plate 60b of the guide member 
60, and the pin 70 stops the rotation of the guide member 60 in the 
direction as shown by the arrow (b) under the influence of the rotation of 
the developing roller 3. 
In the casing 7, the toner storing compartment 8 is arranged. Arranged in 
said toner storing compartment 8 are the agitator 9 and 10 which 
respectively rotate in the direction as shown by the arrow (d). They 
transport the toner while preventing the accommodated toner from 
solidifying. 
As shown in FIG. 17 (a), the film member 2 is caused to adhere around the 
developing roller 3 by the pressing portion 60a, resulting in that the 
slack portion of the film member 2 concentrates at the opening portion of 
the guide member provided at the side confronting the photoreceptor drum. 
Through this process, the space S is formed between the film member 2 and 
the developing roller 3, so that the film member 2 contacts with the 
photoreceptor 100. 
It is to be noted here that the developing roller 3, the film member 2, and 
the regulating blade 5 or the cleaning blade 6 are selected to satisfy the 
relationship of .mu..sub.1 &gt;.mu..sub.2, wherein the coefficient of 
friction between the external surface of the developing roller 3 and the 
internal surface of the film member 2 is .mu..sub.1, that between the 
external surface of the film member 2 and the regulating blade 5 or the 
cleaning blade 6 is .mu..sub.2. Accordingly, in synchronism with the 
rotation of the developing roller 3 in the direction of an arrow (b), the 
film member 2 also rotates in the same direction. 
The developing roller, the film member, the regulating blade and the toner 
used in the developing device of the fourth embodiment are similar in 
materials to the ones used in the developing device of the first 
embodiment. 
The operation of the developing device 1 having the above described 
construction will be explained hereinafter. 
As shown in FIG. 16 (a), and FIGS. 17 (a) and (b), during the development, 
the developing roller 3 rotates in the direction as shown by the arrow 
(b). The pin 70 fixes the end of the support plate 60b of the guide member 
60 trying to rotate in the direction as shown by the arrow (b) under the 
influence of the rotation of the developing roller in order to inhibit the 
rotation of the guide member 60. As a result, the guide member is caused 
to stop at the opposite side of the developing roller with respect to the 
side confronting the photoreceptor. Accordingly, as shown in FIG. 16 (a), 
on condition that the developing roller 3, the toner supply 9 and the 
agitator 10 are caused to rotate by a driving means 30 shown in FIG. 2 (a) 
respectively in directions as shown by the arrows (b) and (d), the toner 
To accommodated within the toner storing compartment 8 is forcibly moved 
in a direction shown by the arrow (d) under an effect of stirring by the 
toner supply 9 and the agitator 10. 
Meanwhile, the film member 2 is driven to rotate in the direction as shown 
by the arrow (b) under the influence of frictional force exerting between 
it and the developing roller 3. The toner To accommodated within the toner 
storing compartment 8, which is in contact with the film member 2, is 
caused to adhere to the surface of the film member 2 by the action of 
electrostatic force, and then, is transported in the direction as shown by 
the arrow (b). When the toner To, held on the surface of the film member 
2, reaches the portion pressed by the regulating blade 5 on the surface of 
the developing roller 3, the toner To is applied uniformly in the form of 
a thin layer on the surface of the film member 2 and charged through the 
friction therewith. 
The toner To of the thin layer held on the surface of the film member 2 
under the influence of its own electrostatic force, which forms a toner 
image to be developed through the a process similar to the first 
embodiment. 
Since the film member 2 in contact with the photoreceptor drum 100 is never 
brought into contact with the developing roller due to the existence of 
the space S, the film member 2 softly and uniformly contacts with the 
photoreceptor drum 100 through its suitable nip width so that the latent 
image formed on the photoreceptor drum 100 may be turned to the uniform 
toner image. In the case where a peripheral speed of the photoreceptor 
drum 100 is caused to differ from that of the film member 2, the toner 
image once formed on the photoreceptor drum 100 can never be broken by 
physical force such as rubbing force or the like. In particular, in the 
case where the peripheral speed of the film member 2 is set faster than 
that of the photoreceptor drum 100, the density of an image can be 
increased, so that fogging can be effectively prevented in a non-image 
portion. 
The toner To having passed the developing region X is successively 
transported, together with the film member 2, in the direction as shown by 
the arrow (b). When the toner To passes between the cleaning blade 6 and 
the film member 2, an image pattern from which the toner To has already 
been consumed in the developing region X is erased so that the uniformity 
of the toner layer may be obtained. 
Subsequently, the toner is supplied again on the surface of the film member 
2 by the rotation of the toner supply 9, and then, the aforementioned 
operation is repeated thereafter. 
Meanwhile, in the case where the development by the developing roller 3 is 
not carried out, as shown in FIG. 16 (b) and FIGS. 18 (a) and (b), the 
developing roller rotates contrarily (rotates in a direction as shown by 
an arrow (b')) following once stopping its rotation, and then, stops the 
driving after a predetermined time has passed. Therefore, the guide member 
60 rotates for substantially half rotation under the influence of the 
contrary rotation of the developing roller 3 in order to contact with the 
above-mentioned pin 70 at the end opposite the end at which the developing 
roller contacts with the pin during the development, and stops. In short, 
the guide member 60 is located at the side confronting the photoreceptor 
100, so that the slack portion of the film member 2 is formed at the 
opposite side of the developing roller to the side confronting the 
photoreceptor. Through this process, the contact between the film member 2 
and the photoreceptor is released. 
FIG. 19 is a cross-sectional view of two developing devices of the fourth 
embodiment disposed around the photoreceptor. In a first developing device 
72, the development is not carried out. Accordingly, the developing roller 
stops after rotating contrarily, the guide member 60 is located at the 
side confronting the photoreceptor so as to prevent the film member 2 from 
contacting with the photoreceptor 100. On the other hand, in a second 
developing device 73, the developing roller rotates in the direction as 
shown by the arrow (b). The pin inhibits the rotation of the guide member 
60 trying to rotate in the direction as shown by the arrow (b), and the 
guide member 60 is located in the position opposite to said first 
developing device. As a result, the slack portion of the film member 2 is 
formed at the side of the developing roller 3 confronting the 
photoreceptor, and the film member 2 contacts with the photoreceptor 100 
to perform developing operation. 
As clearly described so far, in the developing device according to the 
present invention, the film member having a peripheral length longer than 
that of the developing roller is loosely mounted around the developing 
roller and, a slack portion is formed between the film member and the 
developing roller at a location confronting the photoreceptor. By such an 
arrangement, the slack portion of the film member is brought into light 
pressure contact with the surface of the photoreceptor so that the toner 
held on the surface of the film member may be supplied onto the 
electrostatic latent image formed on the surface of the photoreceptor. 
Accordingly, the surface of the photoreceptor is prevented from being 
damaged. Furthermore, even when a gap is unevenly formed between the 
developing roller and the photoreceptor member due to respective warp, 
twist or the like, such unevenness is absorbed by the slack portion of the 
film member, thus resulting in that the gap between the developing roller 
and the photoreceptor can be readily adjusted. Moreover, since the toner 
layer formed on the film member is kept in light contact with the 
photoreceptor through its sufficient nip width, the toner image formed on 
the photoreceptor is not broken, even if peripheral speed thereof differs 
from that of the developing roller. Consequently, picture quality can be 
prevented from deteriorating and, a printed image having steady uniform 
density can be obtained. 
In addition, in a toner supply portion where the toner is applied on the 
surface of the film member, since the film member is kept in close contact 
with the developing roller, a thin layer forming member can be brought 
into steady contact with the film member, even when a regulating blade is 
used as the thin layer forming member. Accordingly, in the toner supply 
portion, since the regulating blade can be pressed against the film member 
under sufficient pressure, electrostatic potential of the charged toner 
can be raised up to a desirable value, thereby enabling the thin layer of 
the toner to be formed uniformly. 
On the other hand, the developing device of the present invention enables 
the film member to move smoothly from the side confronting the 
photreceptor to the opposite side by controlling the aforementioned means 
for adhering the film member. Therefore, the operation of the contact and 
the non-contact between the developing roller and the photoreceptor can be 
carried out easily without moving the whole developing device. 
Consequently, the developing device of the present invention facilitates 
the change of a developing device while preventing toner colours from 
mixing, resulting in that multi-colored development can be carried out 
easily. Furthermore, it facilitates the exchange of the toner color and 
the maintenance of an apparatus which makes single-colored development. 
Although the present invention has been fully described by way of examples 
with reference to the accompanying drawings, it is to be noted that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless such changes and modifications depart from the 
scope of the present invention, they should be construed as being included 
therein.