Conveyor device and image forming apparatus Number:7,426,362 from the United States Patent and Trademark Office (PTO) owispatent A toner-conveying device includes a movable plate. The movable plate is movable between a holding position such as to couple a cap of a toner container to a nozzle when the toner container is supported by a container holder, and a retreating position such as not to hinder loading and unloading of the toner container in the container holder. The movable plate is placed in the holding position by a cam when the nozzle is coupled to the cap, and is released and moved to the retreating position while the toner container is being loaded or unloaded. In this structure, the cap can be properly positioned in the conveyor device while ensuring the rigidity of a bag of the container within a practically preferable range, without reducing the convenience for the operator.<H apparatus, Conveyor, Conveyor, device, 7426362.html, Patent, pto, 7426362

Title: Conveyor device and image forming apparatus

Abstract: A toner-conveying device includes a movable plate. The movable plate is movable between a holding position such as to couple a cap of a toner container to a nozzle when the toner container is supported by a container holder, and a retreating position such as not to hinder loading and unloading of the toner container in the container holder. The movable plate is placed in the holding position by a cam when the nozzle is coupled to the cap, and is released and moved to the retreating position while the toner container is being loaded or unloaded. In this structure, the cap can be properly positioned in the conveyor device while ensuring the rigidity of a bag of the container within a practically preferable range, without reducing the convenience for the operator.

Patent Number: 7,426,362 Issued on 09/16/2008 to Takami

Inventors: Takami; Nobuo (Kawasaki, JP)
Assignee: Ricoh Company, Ltd. (Tokyo, JP)

Appl. No.: 11/763,874

Filed: June 15, 2007

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10924873	Aug., 2004	7248824

Foreign Application Priority Data


Aug 25, 2003 [JP]			2003-300342

Current U.S. Class: 399/258 ; 399/119; 399/260

Current International Class: G03G 15/08 (20060101)

Field of Search: 399/258,260,119,120,110,262 222/DIG.1

References Cited [Referenced By]

U.S. Patent Documents


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6871034	March 2005	Muramatsu et al.
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7133629	November 2006	Kita
7184691	February 2007	Kita et al.
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7248824	July 2007	Takami
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2003/0215267	November 2003	Kita
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2004/0131392	July 2004	Matsumoto et al.
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Foreign Patent Documents


1 229 402	Aug., 2002	EP
S61-176564	Nov., 1986	JP
2003-202745	Jul., 2003	JP
WO 2004/027522	Apr., 2004	WO

Primary Examiner: Chen; Sophia S
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

The present divisional application claims the benefit of priority under 35 U.S.C. .sctn.120 to application Ser. No. 10/924,873, filed Aug. 25, 2004, now U.S. Pat. No. 7,248,824, and under 35 U.S.C. .sctn.119 from Japanese Patent Application No. 2003-300342, filed Aug. 25, 2003, the entire contents of both are incorporated herein by reference.

Claims

What is claimed is:

1. An image forming apparatus comprising: a toner cartridge including, a toner outlet configured to discharge toner, and a shutter configured to open and close the toner outlet; an image forming unit configured to form an image; a nozzle configured to contact the toner cartridge and to move the shutter; and a push-back member pivotally mounted to a main body of the image forming apparatus and configured to push the shutter in a direction of the nozzle such that a pivoting of the push-back member causes the push-back member to push on the shutter.

2. The image forming apparatus of claim 1, wherein the shutter is formed in a cylindrical shape.

3. The image forming apparatus of claim 1, wherein the shutter is configured to shift in a horizontal direction to open or close the toner outlet.

4. The image forming apparatus of claim 1, wherein the toner cartridge further comprises: a cap that includes a nozzle-receiving hole configured to receive the nozzle.

5. The image forming apparatus of claim 1, further comprising: a holder pivotally mounted to a main body of the image forming apparatus, the push-back member being within the holder; and an arm pivotally mounted to the holder, the arm pivoting to move the push-back member when the holder is pivoted to an open position.

6. The image forming apparatus of claim 5, further comprising a spring configured to bias the pivot arm, the spring being disposed on a lower side of the pivot arm.

7. The image forming apparatus of claim 1, wherein the push-back member is mounted to a pivot shaft, and the push-back member includes a contact portion configured to contact the shutter.

8. The image forming apparatus of claim 1, wherein: the pivoting of the push-back member causes the push-back member to push on the shutter and to move the shutter to a closed position.

9. A method of discharging toner from a toner cartridge comprising: receiving a nozzle through a nozzle-receiving hole of the toner cartridge; moving a shutter of the toner cartridge with the nozzle to open a toner outlet of the toner cartridge; discharging toner through the toner outlet of toner cartridge; and pivoting a push-back member which causes the push-back member to push against the shutter.

10. The method of claim 9, wherein the shutter is formed in a cylindrical shape.

11. The method of claim 9, further comprising: shifting the shutter in a horizontal direction to open or close the toner outlet.

12. The method of claim 9, further comprising: pivoting to an open position a holder of the toner cartridge relative to a main body of an image forming apparatus, the push-back member being within the holder, wherein the pivoting of the holder causes an arm which is pivotally mounted to the holder to push the push-back member and move the shutter to the closed position.

13. The method of claim 12, further comprising biasing the arm with a spring disposed on a lower side of the arm.

14. The method of claim 9, wherein the pivoting pivots the push-back member on a pivot shaft such that a contact portion of the push-back member contacts the shutter.

15. The method of claim 9, wherein the pivoting of the push-back member causes the push-back member to push against the shutter and to move the shutter to a closed position.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a conveyor device for conveying, for example, powder, liquid, or gas stored in a flexible container to other devices, and to an image forming apparatus that uses the conveyor device as a toner-conveying device.

2. Description of the Related Art

This type of conveyor device is used in various technical fields. For example, conveyor devices disclosed in Japanese Unexamined Patent Application Publication Nos. 2001-194907, 2001-324863, and 2002-72649 are used in the field of an image forming apparatus. These conveyor devices are used as toner-conveying devices that supply toner from a toner container to a developing device. The toner container mounted in the toner-conveying devices is made of a bag-shaped flexible material, and can be contracted and reduced in volume by a suction force of a suction pump. The shape and size of a hard toner container, such as a cartridge or a bottle, does not change with use. In contrast, the volume of the toner container disclosed in the above publications decreases with use. Therefore, this toner container is easier for the user to handle after use than the hard bottle container. Moreover, it is possible to reduce the cost of transporting the toner container from the user to a manufacturer in order to replace the used toner container by a new one for reclaiming.

In such a flexible toner container, a cap made of, for example, plastic is generally mounted at an opening provided in a flexible bag. In order to supply toner to the developing device, the toner container is loaded in the toner-conveying device, and the cap of the toner container is then engaged with a nozzle (conveying-path forming member) of the toner-conveying device. The interior of the toner container thereby communicates with the conveying path in the toner-conveying device. Toner stored in the toner container is conveyed to the developing device through the conveying path by a suction force of the suction pump.

When the flexible toner container is loaded in the toner-conveying device, the cap must be properly placed in a predetermined position (setting position) in the toner-conveying device so as to be coupled to the nozzle in a normal manner. However, the cap frequently collides with or is pushed by other things during distribution and handling before loading. Since the bag of the toner container is flexible, the posture of the cap is interfered with by such a collision or push.

FIG. 13 is a side view showing an example of a toner container in which a cap is in an incorrect posture. A bag of the toner container has folds on its side faces (front and rear sides of the plane of the figure) so as to take a predetermined shape after volume reduction. However, folds are not provided on front and rear faces (left and right sides of the plane of the figure) of the bag. For this reason, the front and rear faces of the bag have a flexural rigidity lower than that of the side faces. Therefore, the cap tends to tilt toward the front or rear face of the bag and interferes with its posture, as shown in FIG. 13. In particular, since a portion of the bag near the cap is tapered so that inner toner easily concentrates at the cap during a toner supply operation, the posture of the cap is prone to be interfered with.

When the toner container having the cap in an incorrect posture is loaded in the toner-conveying device, the cap is not placed in a predetermined position inside the toner-conveying device. Therefore, the nozzle of the toner-conveying device is not properly coupled to the cap, and a normal toner supply operation cannot be performed. Although the operator can correct the posture of the cap before loading, this is troublesome for the operator, and convenience for the operator is substantially reduced.

Even when the cap is in a correct posture before loading, if the cap collides with something while the toner container is being loaded in the toner-conveying device, the posture of the cap is easily interfered with because the bag of the toner container is flexible. Therefore, the operator also must take care so that the posture of the cap will not be interfered with during loading of the toner container, and this reduces convenience.

While the operator generally loads the toner container while holding the bag, it is difficult for the operator to correct the posture of the cap by handling the held portion. Since the bag is flexible, a force applied to the held portion by the operator is not easily transmitted to the cap, and it is difficult for the operator holding the bag to control the position and posture of the cap.

In order to properly place the cap in a predetermined position without reducing the convenience for the operator, two methods for preventing interference with the posture of the cap can be adopted.

More specifically, a first method is to increase the thickness of the bag for higher rigidity. In this method, however, since a sheet material that forms the bag is thick, heat is not easily transmitted to the inner side of the sheet material during a seam-welding process for welding a seam of the sheet. For this reason, welding failure may occur, or the strength may decrease. In order to prevent welding failure or a decrease in strength, time taken for the seam-welding process must be increased, and the manufacturing cost of the bag increases. When the posture of the cap is interfered with by an external force for some reason, creases are made and clearly remain after the posture is corrected. Consequently, the bag does not take a desired shape after volume reduction, but deforms into an undesirable shape along the creases.

A second method is to reduce the rigidity of the bag so that the posture of the cap is easily corrected. In this method, however, the thickness of the sheet material of the bag is reduced, and a portion of the bag near the cap is first crushed at the early stage of the volume reduction process. When the portion is crushed, discharging of toner from the toner container is hindered, the amount of toner to be discharged varies, and much toner remains in the toner container. Furthermore, since the operator generally holds the bag, as described, when the bag is too soft, ease of handling and convenience are reduced.

From the above viewpoints, there is a practically desirable range of rigidity of the bag in the toner container, and it is difficult to overcome the above problems in the range by preventing the posture of the cap from being interfered with.

The above problems occur not only to the mechanism for supplying toner from the toner container to the developing device, but also to a mechanism for conveying a material stored in a container made of a flexible material to other devices.

SUMMARY OF THE INVENTION

In view of the above-described background, an object of the present invention is to provide a conveyor device in which the rigidity of a bag of a container is within a practically preferable range, and a cap of the container can be placed in the right position without reducing convenience for the operator, and to provide an image forming apparatus including the conveyor device.

In order to achieve the above object, according to an aspect, the present invention provides a conveyor device including a container support for supporting a detachable container in which a substance stored in a flexible bag is discharged through a cap provided at an opening of the bag while an external pressure is applied to the bag or the inner pressure of the bag is reduced in order to deform the bag and to reduce the volume of the bag; a conveying-path forming member that is to be coupled to the cap of the container supported by the container support and that defines a conveying path in which the substance discharged from the container is conveyed to a destination; a cap holder movable between a holding position such as to movable between a holding position such as to couple the cap of the container to the conveying-path forming member when the container is supported by the container support, and a retreating position such as not to hinder loading and unloading of the container into and from the container support; and a positioning unit for placing the cap holder in the holding position.

Preferably, when the container is supported by the container support, a portion of the bag having a relatively low flexural rigidity near the cap faces in a direction that substantially coincides with a moving direction of the cap holder.

Preferably, the conveying-path forming member is inserted in the cap substantially in a moving direction of the cap holder to form the conveying path.

Preferably, the conveyor device further includes a conveying-path-forming-member driving mechanism that moves the conveying-path forming member between a coupled position and an uncoupled position. The conveying-path forming member is coupled to the cap of the container supported by the container support at the coupled position, and does not hinder loading and unloading of the container into and from the container support at the uncoupled position. The cap holder is placed in the holding position by the positioning unit in response to a motion of the conveying-path-forming-member driving mechanism for moving the conveying-path forming member from the uncoupled position to the coupled position, and the positioning of the cap holder by the positioning unit is released in response to a motion of the conveying-path-forming-member driving mechanism for moving the conveying-path forming member from the coupled position to the uncoupled position.

Preferably, the conveyor device further includes a container-support driving mechanism that moves the container support between a loading position at which the container is loaded into or unloaded from the container support and a stored position at which the container supported by the container support is stored in the conveyor device. The conveying-path-forming-member driving mechanism moves the conveying-path forming member from the uncoupled position to the coupled position in response to a motion of the container-support driving mechanism for moving the container support from the loading position to the stored position, and moves the conveying-path forming member from the coupled position to the uncoupled position in response to a motion of the container-support driving mechanism for moving the container support from the stored position to the loading position.

Preferably, the movement of the conveying-path forming member from the uncoupled position to the coupled position is completed after the cap holder is placed in the holding position by the positioning unit.

Preferably, the conveyor device further includes a container-support driving mechanism that moves the container support between a loading position at which the container is loaded into or unloaded from the container support and a stored position at which the container supported by the container support is stored in the conveyor device. The cap holder is placed in the holding position by the positioning unit in response to a motion of the container-support driving mechanism for moving the container support from the loading position to the stored position, and the cap holder is released from the positioning unit in response to a motion of the container-support driving mechanism for moving the container support from the stored to the loading position.

Preferably, when the conveying-path forming member is inserted in a through hole of the cap communicating with the opening so as to change places with a shutter mounted in the cap that plugs the through hole, the conveying path communicates with the opening.

Preferably, a direction of insertion of the conveying-path forming member is substantially orthogonal to a loading and unloading direction of the container into and from the container support.

Preferably, the cap holder is released from the positioning unit after the shutter member returns in the through hole so as to change places with the cap.

Preferably, the conveyor device further includes a conveying-path-forming-member driving mechanism that moves the conveying-path forming member between a coupled position and an uncoupled position, the conveying-path forming member being coupled to the cap of the container supported by the container support at the coupled position and not hindering loading and unloading of the container into and from the container support at the uncoupled position; and a cap moving mechanism that moves the cap in a coupling direction in response to a motion of the conveying-path-forming-member driving mechanism for moving the conveying-path forming member from the uncoupled position to the coupled position and that moves the cap in a direction opposite to the coupling direction in response to a motion of the conveying-path-forming-member driving mechanism for moving the conveying-path forming member from the coupled position to the uncoupled position.

Preferably, the conveying-path-forming-member driving mechanism is a link mechanism.

According to another aspect, the present invention provides a conveyor device including a container support for supporting a detachable container in which a substance stored in a flexible bag is discharged through a cap provided at an opening of the bag while an external pressure is applied to the bag or the inner pressure of the bag is reduced in order to deform the bag and to reduce the volume of the bag; a conveying-path forming member that is to be coupled to the cap of the container supported by the container support and that defines a conveying path in which the substance discharged from the container is conveyed to a destination; a conveying-path-forming-member driving mechanism that moves the conveying-path forming member between a coupled position and an uncoupled position, the conveying-path forming member being coupled to the cap of the container supported by the container support at the coupled position and not hindering loading and unloading of the container into and from the container support at the uncoupled position; and a cap moving mechanism that moves the cap in a coupling direction in response to a motion of the conveying-path-forming-member driving mechanism for moving the conveying-path forming member from the uncoupled position to the coupled position and that moves the cap in a direction opposite to the coupling direction in response to a motion of the conveying-path-forming-member driving mechanism for moving the conveying-path forming member from the coupled position to the uncoupled position.

Preferably, the conveyor device conveys toner stored in the container to a developing device provided in an image forming apparatus.

According to a further aspect, the present invention provides an image forming apparatus including a developing device that develops a latent image formed on a latent-image bearing member with toner to form a toner image, and that transfers the toner image onto a recording medium to form an image; a container that stores the toner conveyed to the developing device; and the above conveyor device for conveying the toner from the container to the developing device.

In the conveyor device and the image forming apparatus described above, the cap holder can be placed in the holding position by the positioning unit when the conveying-path forming member is coupled to the cap. Therefore, the cap of the container supported by the container support is held in the right position by the cap holder. Accordingly, the cap and the conveying-path forming member can be properly coupled, and a normal toner supply operation is achieved.

The holding position refers to a proper setting position for the cap, in general, a position at which the cap lies in a correct posture when the container is supported by the container support. Therefore, when the posture of the cap is correct, even when the cap holder is fixedly placed in the holding position, the cap can be held in the proper setting position. However, when the cap holder is thus fixedly positioned, a region in which the cap can lie when the container is supported in the container holder (hereinafter referred to as a "setting region") is limited to a region in which the cap lies in a correct posture. In this case, in a state in which the posture of the cap is interfered with, when the container is supported by the container holder, the cap is obstructed by the cap holder and cannot enter the setting region. As a result, the cap cannot be held in the proper setting position, and a normal toner supply operation cannot be achieved.

Accordingly, in the conveyor device of the present invention, the cap holder is movable to the retreating position such as not to hinder loading and unloading of the container into and from the container support. Therefore, the cap holder can be moved to the retreating position by releasing the positioning by the positioning unit when loading and unloading the container into and from the container holder. In this case, even when the cap of the container is in an incorrect posture, it is not obstructed by the cap holder, and the container can be reliably supported by the container holder. More specifically, when the cap holder moves to the retreating position, the setting region is thereby enlarged, and so-called "play" is produced in the region. Even when the posture of the cap is interfered with, if the interference is within the play, the cap can enter the setting region when the container is supported by the container holder. After the container is thus supported by the container support, the cap holder can be placed in the holding position by the positioning unit, and the cap can be held in a proper setting position. Therefore, even when the cap is in an incorrect posture, the operator can load the container in the container holder without correcting the posture. Moreover, the cap is reliably coupled to the conveying-path forming member, and a normal toner supply operation is achieved.

The container can be loaded and unloaded as long as the cap holder is released from positioning in the holding position. Therefore, the cap holder may be movable between the holding position and the retreating position, or may positively move to the retreating position. In the former case, the cap can push the movable cap holder toward the retreating position when loading and unloading the container. Therefore, the cap is not obstructed by the cap holder.

As described above, the container having the cap in an incorrect posture can be loaded in the conveyor device and the cap can be held at a proper setting position by improving the configuration of the conveyor device. Therefore, the cap can be placed a right setting position in the conveyor device while maintaining the rigidity of the bag of the container within a practically preferable range, without reducing the convenience for the operator.

Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic structural view of a printer according to an embodiment of the present invention;

FIG. 2 is an enlarged view schematically showing the configuration of a yellow process unit in the printer;

FIG. 3 is a perspective view of a yellow-toner container;

FIG. 4 is a schematic structural view showing a yellow-toner conveying device and a part of a yellow-toner developing device;

FIG. 5 is an explanatory view showing a state of the yellow toner container after volume reduction;

FIG. 6 is an exploded perspective view of an example of a cap of the yellow-toner container;

FIG. 7 is an exploded perspective view of another example of a cap of the yellow-toner container;

FIG. 8 is a perspective view of the printer;

FIG. 9 is a perspective view of a container holder in the yellow-toner conveying device;

FIGS. 10A and 10B are vertical cross-sectional views of the yellow-toner conveying device, taken along a nozzle-receiving hole of the cap, respectively shoring a state in which the container holder is opened and a state in which the container holder is closed;

FIGS. 11A and 11B are explanatory views of a driving mechanism for turning a cam, respectively showing a state in which the container holder is opened and a state in which the container holder is closed;

FIGS. 12A and 12B are explanatory views of a nozzle-driving mechanism, respectively showing a state in which the container holder is opened and a state in which the container holder is closed; and

FIG. 13 is a side view of a toner container having a cap in an incorrect posture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to FIG. 1, a tandem color laser printer (hereinafter simply referred to as a "printer") including a plurality of photosensitive members arranged side by side will be described below as an image forming apparatus according to an embodiment of the present invention.

First, the basic configuration of the printer will be described.

FIG. 1 is a schematic structural view of the printer of this embodiment. The printer includes four process units 1Y, 1M, 1C, and 1K for forming images of yellow (Y), magenta (M), cyan (C), and black (K). Letters Y, M, C, and K following reference numerals of the components indicate that the components are provided, respectively, for yellow, magenta, cyan, and black. The printer also includes an optical writing unit 10, an intermediate transfer unit 11, a secondary transfer bias roller 18, a pair of register rollers 19, a sheet cassette 20, and a belt-type fixing unit 21.

The optical writing unit 10 includes a light source, a polygonal mirror, an f-.theta. lens, and a reflecting mirror, and applies laser light on the surfaces of photosensitive members, which will be described later, according to image information.

FIG. 2 is an enlarged view schematically showing the configuration of the yellow process unit 1Y of the above-described process units 1Y, 1M, 1C, and 1K. Since the other process units 1M, 1C, and 1K have the same configuration as that of the yellow process unit 1Y, descriptions thereof are omitted. As shown in FIG. 2, the process unit 1Y includes a photosensitive drum 2Y, a charger 30Y, a developing device 40Y, a drum-cleaning device 48Y, and a discharger (not shown).

The charger 30Y uniformly charges the surface of the photosensitive drum 2Y in the dark by bringing a charging roller 31Y, to which an AC voltage is applied, into sliding contact with the sensitive drum 2Y. The charged surface of the photosensitive drum 2 is scanned with laser light modulated and deflected by the optical writing unit 10, thereby forming an electrostatic latent image thereon. The electrostatic latent image is developed into a yellow toner image by the developing device 40Y.

The developing device 40Y includes a developing roller 42Y with its peripheral surface partly exposed from an opening of a development case 41Y. The developing device 40Y also includes a first conveyor screw 43Y, a second conveyor screw 44Y, a doctor blade 45Y, a toner-concentration sensor (hereinafter referred to as a "T-sensor") 46Y.

The development case 41Y stores a two-component developing agent (not shown) containing magnetic carriers and yellow toner particles to be negatively charged. The two-component developing agent is frictionally charged while being agitated and conveyed by the first conveyor screw 43Y and the second conveyor screw 44Y, and is then placed on the surface of the developing roller 42Y. The two-component developing agent is conveyed to a developing region opposing the photosensitive drum 2Y after its layer thickness is regulated by the doctor blade 45Y, and yellow toner particles are adsorbed on an electrostatic latent image formed on the photosensitive drum 2Y to form a yellow toner image. The two-component developing agent from which the yellow toner particles are reduced by development is returned into the development case 41Y with the rotation of the developing roller 42Y.

A partition 47Y is provided between the first conveyor screw 43Y and the second conveyor screw 44Y. The partition 47Y separate the interior of the development case 41Y into a first supply section that includes the developing roller 42Y and the first conveyor screw 43Y, and a second supply section that includes the second conveyor screw 44Y. The first conveyor screw 43Y is rotated by a driving means (not shown) to convey a two-component developing agent in the first conveying section from the front side of the plane of the figure to the back side and to supply the agent to the developing roller 42Y. The two-component developing agent conveyed to the adjacency of an end of the first supply section by the first conveyor screw 43Y enters the second supply section through an opening (not shown) provided in the partition 47Y. In the second supply section, the second conveyor screw 44Y is rotated by a driving means (not shown) to convey the two-component developing agent supplied from the first supply section in an direction opposite from the conveying direction of the first conveyor screw 43Y. The two-component developing agent is conveyed near an end of the second supply section, and returns into the first supply section through another opening (not shown) provided in the partition 47Y.

The T-sensor 46Y is formed of a magnetic-permeability sensor, and is provided on a bottom wall at almost the center of the second supply section to output a voltage corresponding to the magnetic permeability of the two-component developing agent passing thereon. Since the magnetic permeability of the two-component developing agent has some correlation with the toner concentration, the T-sensor 46Y outputs a voltage corresponding to the yellow toner concentration. The output voltage is sent to a control unit (not shown). The control unit includes a RAM that stores a target output voltage Y-Vtref from the T-sensor 46Y. The RAM also stores target output voltages M-Vtref, C-Vtref, and K-Vtref from T-sensors (not shown) mounted in the other developing devices. The value Y-Vtref is used to control the driving a yellow-toner conveying device. More specifically, the control unit supplies yellow toner into the above-described second supply section while controlling the driving of the yellow-toner conveying device so that the output voltage from the T-sensor 46Y becomes close to Y-Vtref. By this supply, the concentration of yellow-toner in the two-component developing agent in the developing device 40Y is maintained within a predetermined range. Similar toner supply control is executed in the developing devices of the other process units.

A yellow toner image formed on the photoconductive drum 2Y is transferred onto an intermediate transfer belt (not shown) which will be described later. After intermediate transfer, the surface of the photosensitive drum 2Y is cleaned of residual toner by the drum-cleaning device 48Y, and is discharged by a discharging lamp. Then, the surface of the photosensitive drum 2Y is uniformly charged by the charger 30Y for the next image-forming operation. This also applies to the other process units.

Referring again to FIG. 1, the intermediate transfer unit 11 includes an intermediate transfer belt 12, a driving roller 13, belt-stretching rollers 14 and 15, a belt cleaner 16, and four intermediate transfer bias rollers 17Y, 17M, 17C, and 17K. The intermediate transfer belt 12 is tightly stretched around the driving roller 13 and the belt-stretching rollers 14 and 15, and is moved counterclockwise in an endless manner by the driving roller 13 that is rotated by a driving system (not shown). An intermediate transfer bias is applied from a power supply (not shown) to the four intermediate transfer bias rollers 17Y, 17M, 17C, and 17K. The intermediate transfer belt 12 is pressed against photosensitive drums 2Y, 2M, 2C, and 2K from the back side to form intermediate transfer nips therebetween. At the intermediate transfer nips, intermediate transfer fields are formed between the photosensitive drums 2Y, 2M, 2C, and 2K and the intermediate transfer bias rollers 17Y, 17M, 17C, and 17K by the influence of the intermediate transfer bias. A yellow toner image formed on the photosensitive drum 2Y is transferred onto the intermediate transfer belt 12 by the intermediate transfer field and a nip pressure. Magenta, cyan, and black toner images formed on the photosensitive drums 2M, 2C, and 2K are sequentially transferred on the yellow toner image, thus forming a superimposed toner image on the intermediate transfer belt 12. The superimposed toner image is secondarily transferred onto a transfer paper sheet P serving as a recording medium at a secondary transfer nip which will be described later. On the other hand, toner remaining on the surface of the intermediate transfer belt 12 passing through the secondary transfer nip is removed by the belt cleaner 16 that is in contact with a portion of the intermediate transfer belt 12 backed by the belt-stretching roller 15.

The sheet cassette 20 is provided below the optical writing unit 10, and accommodates a plurality of stacked transfer paper sheets P. A supply roller 20a is in pressed contact with the uppermost transfer paper sheet P. When the supply roller 20a rotates at a predetermined timing, the uppermost transfer paper sheet P is supplied to a sheet-feeding path.

The secondary transfer bias roller 18 is in contact with the driving roller 13 of the intermediate transfer unit 11 with the intermediate transfer belt 12 therebetween, thus forming a secondary transfer nip. A secondary transfer bias is applied from a power supply (not shown) to the secondary transfer bias roller 18.

A transfer paper sheet P supplied from the sheet cassette 20 to the sheet-feeding path is nipped between the register rollers 19. On the other hand, a superimposed toner image formed on the intermediate transfer belt 12 enters the secondary transfer nip with the endless motion of the intermediate transfer belt 12. The register rollers 19 deliver the nipped transfer paper sheet P at a timing such that the transfer paper sheet P can be brought into tight contact with the superimposed toner image at the secondary transfer nip. The superimposed toner image is thereby brought into tight contact with the transfer paper sheet P at the secondary transfer nip. The superimposed toner image is secondarily transferred onto the transfer paper sheet P by the secondary transfer bias and the nip pressure, and forms a full-color image in connection with white color of the transfer paper sheet P. The transfer paper sheet P on which the full-color image is thus formed is conveyed to the fixing unit 21.

The fixing unit 21 includes a belt unit 21b in which a fixing belt 21a tightly stretched by three rollers is moved in an endless manner, and a heating roller 21c having a heat source therein. The full-color image is fixed while nipping the transfer paper sheet P between the belt unit 21b and the heating roller 21c. The transfer paper sheet P passing through the fixing unit 21 is ejected out of the printer through a pair of ejection rollers 22.

In the printer having the above-described configuration, the process units 1Y, 1M, 1C, and 1K, the intermediate transfer unit 11, and so on constitute a visible-image forming means that forms a toner image as a visible image on a transfer paper sheet P as a recording medium.

A description will now be given of toner containers 50Y, 50M, 50C, and 50K that respectively store yellow, magenta, cyan, and black toners to be supplied.

FIG. 3 is a perspective view of the toner container 50Y for yellow toner. The toner container 50Y includes a flexible bag 51Y, a cap 52Y, and a cylindrical shutter 53Y. The bag 51Y is a square bag made of a single or a plurality of deformable and flexible sheet materials having a thickness of approximately 50 .mu.m to 210 .mu.m, and stores yellow toner. The sheet material is, for example, a resin sheet of polyester, polyethylene, or nylon, or a paper sheet. In this embodiment, the bag 51Y has two layers, that is, an inner layer made of a polyethylene sheet to which the cap 52Y can be welded, and an outer layer made of a nylon sheet to cover the inner layer. Reinforcing layers 80 made of, for example, polyethylene terephthalate or aluminum are provided on outer flat portions of the front and rear faces (front and rear sides of the plane of the figure) of the bag 51Y.

Since the flat portions are maintained flat by the action of the reinforcing layers 80 during a volume reduction process of the bag 51Y, they will not be crinkled and waved. Consequently, folds f are not disturbed by crinkling and waving, and the bag 51Y can be neatly folded along the folds f after volume reduction.

Each of the reinforcing layers 80 has eight holes, as shown in FIG. 3. The operator can hold the bag 51Y with the fingers put in the holes. Therefore, high efficiency is ensured when the operator holds and shakes the toner container 50Y and loads the toner container 50Y in a container holder which will be described later. Furthermore, these holes also function as marks that indicate to the operator proper positions at which the fingers should be placed to hold the bag 51Y. Accordingly, the operator can properly hold the bag 51Y without disturbing the folds f, and the bag 51Y can take a fixed shape after volume reduction.

In an expanded state, the upper half of the bag 51Y is shaped like a substantially rectangular parallelepiped, and the lower half is shaped like an inverse quadrangular pyramid (tapered). This shape of an inverse quadrangular pyramid defines a hopper that is inclined downward toward the cap 52Y. The cap 52Y, which is made of, for example, resin and does not deform, is welded to the leading end of the hopper. The toner container 50Y is used with the cap 52Y down, and the bag 51Y communicates with the cap 52Y. A nozzle-receiving hole 54Y horizontally extends through the cap 52Y, and a cylindrical shutter 53Y is fitted in the nozzle-receiving hole 54Y to seal yellow toner in the toner container 50Y. While only the toner container 50Y for yellow toner has been described with reference to FIG. 3, the toner containers 50M, 50C, and 50K for other color toners have a similar structure, and therefore, descriptions thereof are omitted.

A description will now be given of the configuration and operation of a toner-conveying device for conveying supply toner to each developing device.

FIG. 4 is a schematic structural view showing a toner-conveying device for yellow toner and a part of the developing device for yellow toner. The toner-conveying device includes a conveying tube 70Y, a nozzle 71Y that defines a conveyor path, a suction pump 90Y, and a container holder (not shown) serving as a container support for supporting the toner container 50Y. The toner container 50Y is loaded in the container holder with the cap 52Y facing down, and is replaced by new one when toner is almost consumed. In this case, the leading end of the nozzle 71Y is fitted in a nozzle-receiving hole 54Y of a cap 52Y of a new toner container 50Y in which a shutter 53Y shown in FIG. 3 is engaged. Consequently, the shutter 53Y is pushed out of the nozzle-receiving hole 54Y, and the nozzle 71Y engages with the nozzle-receiving hole 54Y and is coupled to the cap 52Y. As a result, a toner-conveying path is formed to convey yellow toner discharged form the toner container 50Y to the developing device 40Y.

The conveying tube 70Y is connected to the rear end of the nozzle 71Y, and is made of, for example, a rubber or resin material that is deformable and toner-resistant, and has an inner diameter of 4 mm to 10 mm. The conveying tube 70Y is connected to a pump unit 91Y of the suction pump 90Y at an end remote from the nozzle 71Y. The suction pump 90Y is a uniaxial eccentric screw pump (popularly called a Mono pump), and includes the pump unit 91Y, an outlet 95Y communicating with the pump unit 91Y, a shaft 96Y, a universal joint 97Y, and a suction motor 98Y.

The pump unit 91Y of the suction pump 90Y includes a rotor 92Y formed of an eccentric double-thread screw made of metal or resin having high rigidity, a stator 93Y made of, for example, rubber and having a cavity shaped like a double-thread screw, and a suction inlet 94Y. When the suction motor 98Y rotates, the rotational force is transmitted to the rotor 92Y through the universal joint 97Y and the shaft 96Y. The rotor 92Y then rotates inside the stator 93Y, and a negative pressure is produced at the suction inlet 94Y of the pump unit 91Y. Yellow toner in the bag 51Y is sucked into the suction pump 90Y by the negative pressure through the conveying tube 70Y, the nozzle 71Y, and the cap 52Y. Subsequently, the yellow toner is discharged into the outlet 95Y through the stator 93Y. The outlet 95Y is connected to the second supply section of the developing device 40Y, and the yellow toner is supplied from the outlet 95Y to the second supply section to be mixed with a two-component developing agent (not shown).

The toner-conveying device for conveying yellow toner by the suction of the suction pump 90Y in this way does not need a moving member, such as an auger, for applying a moving force to the yellow toner in the toner container 50Y. Therefore, the structure of the toner container 50Y is simplified, and the weight thereof is reduced. Moreover, the volume of the toner container 50Y can be reduced by deflating the deformable bag 51Y by a suction force of the suction pump 90Y. When the used toner container 50Y is taken back by, for example, a manufacturer for recycle, the cost of transporting the toner container 50Y can be reduced by the weight reduction and volume reduction. Since it is also unnecessary to place a moving member, such as a screw, in the conveying tube 70Y for conveying the toner, the conveying tube 70Y can be made of a deformable material and can be freely laid out in the printer. This substantially increases the degree of layout flexibility of the toner-conveying path. Even when the toner container 50Y is placed on the lower side of the developing device 40Y in the gravitational direction, the toner can be pumped up and conveyed by the suction force of the suction pump 90Y. This also increases the degree of layout flexibility in the printer.

Preferably, the bag 51Y of the toner container 50Y has folds f, as shown in FIG. 3. In this case, it is possible to deflate the bag 51Y along the folds f by suction and to finally fold the bag 51Y into a substantially planar shape, as shown in FIG. 5. Consequently, the volume of the toner container 50Y is further reduced, and the transport cost is further reduced.

FIG. 6 is an exploded perspective view of an example of a cap 52Y of the toner container 50Y. The cap 52Y includes a main portion 55Y having a large vertical hole and a horizontal nozzle-receiving hole 54Y, a welding portion 56Y of circular cross section protruding from the upper surface of the main portion 55Y, and a cap portion 57Y to be fitted in the vertical hole of the main portion 55Y from below. The welding portion 56Y is welded to the opening of the above-described bag 51Y in order to fix the cap 52Y to the bottom of the bag 51Y. The cap portion 57Y also has a nozzle-receiving hole 54Y. That is, the nozzle-receiving hole 54Y horizontally extends through the main portion 55Y and the cap portion 57Y fitted therein. Ring-shaped seals 58Y made of an elastic material, such as rubber, are fixed at both ends of the nozzle-receiving hole 54Y of the cap portion 57Y. Accordingly, when the nozzle 71Y and the shutter 53Y are put in the nozzle-receiving hole 54Y, the interior of the nozzle-receiving hole 54 is hermetically sealed.

The cap 52Y is divided into the main portion 55Y and the cap portion 57Y in order to easily fill the bag 51Y with yellow toner. When the main portion 55Y and the cap portion 57Y are combined, yellow toner must be supplied from the narrow nozzle-receiving hole 54Y that extends at an angle of 90.degree. to the toner path leading from the bag 51Y. In contrast, when the main portion 55Y and the cap portion 57Y are separate, yellow toner can be supplied straight to the bag 51Y from the large hole of the cap 52Y that extends straight from the toner path. Moreover, the ring-shaped seals 58Y can be prevented from being soiled with yellow toner during a toner supply operation. In order to prevent the shutter 53Y from being pushed out of the nozzle-receiving hole 54Y by the finger, it is preferable that the shutter 53Y has a small diameter such as not to be pushed by the finger. The cross-sectional area of the shutter 53Y is preferably set at 8 mm.sup.2 or less, more preferably, 6 mm.sup.2 or less.

FIG. 7 is an exploded perspective view of another example of a cap 52Y of the toner container 50Y. The cap 52Y includes a welding portion 156Y, a main portion 155Y engaged with the welding portion 156Y, and a cap portion 157Y fitted in a vertical hole of the main portion 155Y from above. The welding portion 156Y is welded to the opening of the above-described bag 51Y. By engaging the welding portion 156Y with the main portion 155Y in which the cap portion 157Y is fitted in the vertical hole, the cap 52Y is fixed to the bottom of the bag 51Y. In this case, the top of the cap portion 157Y is fitted in a hole of the welding portion 156, and a gap therebetween is sealed by a ring-shaped seal 58Y. In a normal condition, there is no problem even when the ring-shaped seal 58Y is not provided. However, in a reduced-pressure condition (highland condition), when the ring-shaped seal 58Y is not provided, air leaks from the bag 51Y, and toner packing occurs when the condition returns to the normal condition. In order to prevent toner packing, the ring-shaped seal 58Y is provided in the fitting portion between the top of the cap portion 157Y and the hole of the welding portion 156Y in the toner container 50Y shown in FIG. 7.

A circuit board 159Y is mounted in the main portion 155Y of the cap 52Y. The circuit board 159Y includes, for example, an electric circuit and a memory in order to check the loading of the toner container 50Y and the amount of residual toner from the main body of the printer. When the toner container 50Y is loaded in the main body of the printer, a connecting terminal of the circuit board 159Y touches a connecting terminal of the main body, and information is exchanged between the circuit board 159Y and the main body, so that the presence of the toner container 50Y and the amount of residual toner can be checked.

The configuration of the toner-conveying device, which is a typical characteristic the present invention, will be described below.

FIG. 8 is a perspective view of the printer. Referring to FIG. 8, four container holders 75Y, 75M, 75C, and 75K that turn on pivots (not shown) are provided at the front of a housing of the printer. The container holders 75Y, 75M, 75C, and 75K define toner-conveying devices for the respective color toners, and house and support toner containers for the respective colors. For example, in order to load the toner container 50Y for yellow toner in the container holder 75Y, the operator opens a lock (not shown), and pivots the container holder 75Y forward, as shown in FIG. 8. The operator then drops the toner container 50Y into the container holder 75Y while holding the bag 51Y with both hands so that the cap 52Y faces downward in the vertical direction.

FIG. 9 is a perspective view of the container holder 75 in the toner-conveying device for yellow toner. While the toner-conveying device for yellow toner will be described below as an example, the toner-conveying devices for other color toners have a similar structure. For convenience of explanation, the letters Y, M, C, and K for representing the colors are omitted.

The toner-conveying device includes a fixed portion 76 fixed to the main body of the printer. A pivot shaft 75a is rotatably fixed to the fixed portion 76 at the bottom of the container holder 75. The container holder 75 can thereby turn on the pivot shaft 75a. Projections 75b are provided on both side faces on the upper side of the container holder 75, and are engaged with two slide members 72 turnably attached to the main body of the printer. Both side faces at the lower side of the container holder 75Y are in contact with arms 76a extending from the fixed portion 76, and are provided with stoppers (not shown) that regulate the movement relative to the arms 76a. The opening range of the container holder 75 is regulated by the retention of the slide members 72 by the projections 75b and the retention of the arms 76a by the stoppers. In this way, a holder-driving mechanism serving as the container-support driving mechanism