Patent Abstract:
An image forming apparatus including a development mechanism for developing an electrostatic latent image formed on an image carrying member into a visual image, a toner storage detachably installed and provided for storing toner therein, a toner transporting mechanism for transporting the toner from the toner storage to the development mechanism, and a supporting device for detachably supporting the toner storage therein and moving between a set position at which the toner storage is engaged with the toner transporting mechanism and a tilt position at which the toner storage is disengaged from the toner transporting mechanism.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This patent application is a continuation-in-part application of U.S. patent application Ser. No. 10/412,390 and claims priority to U.S. patent application Ser. No. 10/412,390, filed Apr. 14, 2003, now U.S. Pat. No. 6,882,817, in the United States Patent and trademark Office, and Japanese patent applications, Nos. JPAP 2002-110525 filed on Apr. 12, 2002, and JPAP 2003-38211 filed on Feb. 17, 2003, in the Japanese Patent Office. The entire contents of these documents are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an image forming method and apparatus, and more particularly to an image forming method and apparatus which includes an easy-to-handle large capacity toner container. 
   Conventionally, an electrophotographic image forming apparatus uses a development mechanism which develops an electrostatic latent image formed on an image carrying member into a visual image. In particular, an electrophotographic image forming apparatus using a two-component developer for the development mechanism adopts a specific structure in which a toner storage such as a toner bottle, a toner cartridge, a toner tank, and the like is arranged close to the development mechanism and toner is transported with a transportation mechanism such as an auger. 
   In addition, an electrophotographic image forming apparatus provided with a color capability as a recent trend has four development mechanisms with four toner storages for colors of yellow, magenta, cyan, and black. 
   It is a general requirement for such an image forming apparatus to have a compact size without sacrificing a capacity of the toner storage. However, the toner storage is needed to be arranged close to the development mechanism in an engine of the image forming apparatus and therefore the reduction in size of the engine is constrained. Accordingly, flexibility of a machine design itself is interfered. 
   Japanese Laid-Open Patent Application Publication, No. 2001-305843, describes an image forming apparatus which has a toner storage arranged in a separate unit from a development mechanism since the toner contained in the toner storage is transported to the development mechanism with a screw pump called a mohno-pump. 
   Generally, an image forming apparatuses capable of performing functions of copying, printing, and facsimile, for example, has a relatively large machine size and, in such an apparatus, a dead space (i.e., unutilized space) may often be found underneath an operation panel thereof. If a toner storage is placed in this dead space, a large amount of toner can be stocked in the apparatus without the needs of further enlarging the machine size. However, since the top of this dead space is covered by the operation panel, an exchange of the toner storage is not easily performed. 
   BRIEF SUMMARY OF THE INVENTION 
   In view of the foregoing, it is an object of the present invention to provide a novel image forming apparatus which can store a large capacity of toner without sacrificing exchangeability of a toner storage. 
   Another object of the present invention is to provide a novel image forming method which can store a large capacity of toner without sacrificing exchangeability of a toner storage. 
   To achieve the above-mentioned object, in one example, a novel image forming apparatus includes a development mechanism, a toner storage, and a toner transportation mechanism. The development mechanism is configured to develop an electrostatic latent image formed on an image carrying member into a visual image. The toner storage is detachably installed in the apparatus and is configured to store toner therein. The toner transportation mechanism is configured to transport the toner from the toner storage to the development mechanism. In this apparatus, the toner storage is movable together with at least a part of the toner transportation mechanism between a closed position which is a normal position of the toner storage containing toner and a tilt position at which the toner storage is exchanged with a new toner storage. 
   The toner transportation mechanism may include a flexible tube for transporting the toner from the toner storage to the development mechanism. 
   The toner transportation mechanism may include a screw pump including an elastic stator internally having spiral grooves in a two-screw shape and a rotor rotating inside the stator to transport the toner in an axis direction, and the toner is transported to the development mechanism by an action of a negative pressure generated by the screw pump. 
   The toner storage may be movable between the closed position and the tilt position by a rotational movement. 
   The flexible tube may be arranged near a rotation shaft of the toner storage. 
   The flexible tube may include at least two tube portions joined with a connector arranged near the rotation shaft of the toner storage. 
   At least one of the above-mentioned at least two tube portions included in the flexible tube may be made of a material different from materials of the others. 
   To achieve the above-mentioned object, in one example, a novel image forming method includes the steps of providing, setting, storing, and transporting. The providing step provides a development mechanism developing an electrostatic latent image into a visual image with toner. The setting step sets a toner transportation mechanism. The storing step stores toner in a detachable toner storage. The transporting step transports the toner with the toner transportation mechanism from the detachable toner storage to the development mechanism. In this method, the detachable toner storage is movable together with at least a part of the toner transportation mechanism between a closed position which is a normal position of the detachable toner storage containing toner and a tilt position at which the detachable toner storage is exchanged with a new detachable toner storage. 
   The toner transportation mechanism may include a flexible tube for transporting the toner from the detachable toner storage to the development mechanism. 
   The toner transportation mechanism may include a screw pump including an elastic stator internally having spiral grooves in a two-screw shape and a rotor rotating inside the stator to transport the toner in an axis direction, and the toner is transported to the development mechanism by an action of a negative pressure generated by the screw pump. 
   The detachable toner storage may be movable between the closed position and the tilt position by a rotational movement. 
   The flexible tube may be arranged near a rotation shaft of the detachable toner storage. 
   The flexible tube may include at least two tube portions joined with a connector arranged near the rotation shaft of the detachable toner storage. 
   At least one of the above-mentioned at least two tube portions included in the flexible tube may be made of a material different from materials of the others. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS 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 diagram of a color copying apparatus according to an exemplary embodiment of the present invention; 
       FIG. 2  is a schematic diagram of a major portion of a color copying engine included in the color copying apparatus of  FIG. 1 ; 
       FIG. 3  is a part of the major portion of the color copying engine shown in  FIG. 2  with an enlargement; 
       FIG. 4  is a schematic diagram of a toner replenishing mechanism included in the color copying apparatus of  FIG. 1 ; 
       FIG. 5  is a schematic diagram of a toner replenishing mechanism including a powder pump and a sub-hopper; 
       FIG. 6  is a top view of an upper chamber of the sub-hopper; 
       FIG. 7  is a top view of a lower chamber of the sub-hopper; 
       FIG. 8  is a schematic diagram for showing a tilt position of an enclosure for toner containers in association with the toner replenishing mechanism; 
       FIG. 9  is a schematic diagram of a jointed toner transportation tube for the toner replenishing mechanism; and 
       FIG. 10  is a schematic diagram showing an exemplary structure of the enclosure for the toner containers; 
       FIG. 11  is a diagram of a toner replenishing mechanism for replenishing the development unit of an image forming unit with toner; 
       FIG. 12  is a diagram of a toner container which includes the toner sack and the toner discharging unit; 
       FIG. 13  is a schematic diagram showing a toner discharging unit which includes an upper main body and a lower main body; 
       FIG. 14  is another diagram showing the toner discharging unit which includes the upper main body and lower main body; 
       FIG. 15  is yet another diagram showing the toner discharging unit which includes the upper main body and lower main body; 
       FIG. 16  is a schematic diagram showing an image forming apparatus which includes an enclosure to which the toner container having four toner folders is attached; 
       FIG. 17  is a diagram showing an open and close folder of the enclosure; 
       FIG. 18  is a diagram showing the enclosure which includes the open and close folder which has the separated toner container; 
       FIG. 19  is a diagram showing the enclosure which is pulled out with the handle; 
       FIG. 20  is a diagram showing a nozzle and a slider; 
       FIG. 21  is a diagram showing another exemplary enclosure; 
       FIG. 22  is another diagram showing the enclosure shown in  FIG. 21 ; 
       FIG. 23  is a diagram showing yet another exemplary enclosure; and 
       FIG. 24  is a diagram showing another exemplary toner replenishing mechanism. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In describing the exemplary 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 color copying apparatus  1  is explained, which is one example of a color image forming apparatus according to a preferred embodiment of the present invention. The color copying apparatus  1  forms an image using an electrophotographic method and, as shown in  FIG. 1 , includes a color copying engine  100  at the middle, a sheet supply station  200  at the bottom, and an image scanner  300  at the top of the color copying apparatus  1  with an automatic document feeder (ADF)  400  on top. In addition, the color copying apparatus  1  is also provided with an operation panel  120  in front of and in an integrated form with the image scanner  300 . Those skilled in the art will recognize that the above components may be located at alternative positions within the apparatus in addition to those mentioned above. 
   The color copying engine  100  is provided with a tandem mechanism  10  including four image forming units  11  arranged horizontally for black (Bk), cyan (C), magenta (M), and yellow (Y) colors. Each of the four image forming units  11  includes a photosensitive drum  12  which serves as a primary image carrying member for carrying a latent image formed thereon. Around the photosensitive drum  12 , various requisite mechanisms for the electrophotographic process, as explained herein. 
   Below the tandem mechanism  10 , an intermediate transfer belt  13  is extended under a predetermined tension among a plurality of rollers  14 ,  15 , and  16 , and is arranged to contact the four photosensitive drums  12 . The intermediate transfer belt  13  includes a flexible endless belt and serves as a secondary image carrying member for carrying a toner image. One of the rollers  14 ,  15 , and  16  is driven to rotate the intermediate transfer belt  13  clockwise, as indicated by an arrow. Other rollers which are not directly driven follow the rotation. 
   The color copying engine  100  is further provided with four primary image transfer units  17  which contact an inside surface of the intermediate transfer belt  13  at positions to face the respective photosensitive drums  12  via the intermediate transfer belt  13 . Reference numeral  18  denotes a cleaning unit for removing unused toner particles from the intermediate transfer belt  13 . 
   Above the tandem mechanism  10 , an exposure unit  19  for sequentially irradiating each of the photosensitive drums  12  with an optically-modulated laser beam is provided. The exposure is performed at an area after a charging process and before a development process. Instead of the single exposure unit  19 , four separate exposure units may be provided to be used on a one-to-one basis relative to each of the photosensitive drums  12 . In the exemplary embodiment, the single exposure unit  19  is utilized to decrease cost. 
   Underneath the intermediate transfer belt  13 , a secondary image transfer unit  22  is provided. The secondary image transfer unit  22  includes a secondary image transfer belt  24  which is an endless belt and is extended between two rollers  23 . The secondary image transfer unit  22  is arranged such that a portion of the secondary image transfer belt  24  close to one of the rollers  23  presses the intermediate transfer belt  13  against the roller  16 . Near the other one of the rollers  23  and below the roller  15 , a fixing unit  25  for fixing a toner image carried by and on a recording sheet is provided. 
   The secondary image transfer unit  22  further includes a sheet transport mechanism for transporting a recording sheet carrying a toner image thereon to the fixing unit  25 . As an alternative to the secondary image transfer unit  22 , a non-contact charging unit may be used. With such a non-contact charging unit, a mechanism for transporting a recording sheet carrying a toner image thereon to the fixing unit  25  may be installed separately. 
   The color copying engine  100  is further provided with a pair of sheet ejection rollers  26  for ejecting a recording sheet carrying a toner image fixed thereon and an output tray  27  for storing recording sheets output from the color copying engine  100 . 
   The color copying engine  100  is further provided with a sheet flipping unit  28  for flipping a recording sheet having a front surface already printed so as to print an image on a back side of the recording sheet in a dual surface copying mode. The sheet flipping unit  28  is arranged under the secondary image transfer unit  22  and the fixing unit  25 . 
   When a color copying is performed with the color copying apparatus  100 , a set of originals are placed in a face-up orientation on an original input stacker  30  of the ADF  400 . Alternatively, the set of originals can manually be placed sheet by sheet directly on a contact glass  31  of the image scanner  300 . To do this, the ADF  400  is lifted up since it has a shell-like openable structure and, after the placement of the original, the ADF  400  is lowered to a closing position. 
   Then, upon a depress of a start switch (not shown), when the set of originals are placed on the ADF  400 , an uppermost original of the set of originals is separated and is transported with a sheet transportation mechanism  32  of the ADF  400  to the contact glass  31  of the image scanner  300  and, subsequently, the image scanner  300  is activated. That is, first and second moving units  33  and  34  of the image scanner  300  slide in a predetermined direction. When the original is manually set on the contact glass  31 , the image scanner  300  is immediately activated upon the depress of the start switch. The first moving unit  33  that carries a light source and a mirror (both not shown) causes a light irradiation to move and reflects the light reflected by the original on the contact glass  31 . The second moving unit  34  carrying mirrors (not shown) receives the light reflected by the mirror of the first moving unit  33  and reflects the light to a read sensor  35  via an image forming lens  36 . 
   Also, upon the depress of the start switch, the image forming units  11  are activated to form mono-color images in black, yellow, magenta, and cyan on the respective photosensitive drums  12  in the tandem mechanism  10 . At the same time, the intermediate transfer belt  13  starts to rotate and sequentially receives the mono-color images at a same position thereof, thereby forming a composite color image. 
   Further, upon the depress of the start switch, one of sheet supply rollers  42  of the sheet supply station  200  is started to rotate so that a blank recording sheet is moved to a separation roller  45  in a corresponding sheet stocker  44  among a plurality of sheet stockers  44  provided to a sheet bank  43 . The separation roller  45  separates the recording sheet from the following sheets and transfers it to a transportation passage  46 . Then, the recording sheet is moved to a transportation passage  48  provided to the color copying engine  100  by a plurality of transportation rollers  47 . The recording sheet is then stopped by a pair of registration rollers  49 . 
   When a manual insertion is used, a transportation roller  50  is rotated to move a set of recording sheets placed on a manual insertion tray  51  to a pair of separation rollers  52 . Then, the pair of separation rollers  52  separate an uppermost recording sheet from the rest of the recording sheets and transfers it to the pair of registration rollers  49  through a transportation passage  53 . 
   After that, the pair of registration rollers  49  are started to rotate in synchronism with the movement of the composite color image carried on the intermediate transfer belt  13  and consequently the recording sheet which is blank is inserted between the intermediate transfer belt  13  and the secondary image transfer unit  22 . The composite color image is transferred at one time from the intermediate transfer belt  13  onto the recording sheet by the action of the secondary image transfer unit  22 . 
   After the image transfer, the secondary image transfer unit  22  transports the recording sheet having the composite color image to the fixing unit  25  which then fixes the color image to the recording sheet with heat and pressure. Then, the recording sheet passes through an ejection passage selected by a switch pawl  55  and is ejected to the output tray  27  by the pair of sheet ejection rollers  26 . As an alternative, the recording sheet may be headed to the sheet flipping unit  28  by selecting a transportation passage for the dual surface copying mode with the switch pawl  55 . In this case, the recording sheet is flipped by the sheet flipping unit  28  and is then transported again to the pair of registration rollers  49  in a face-down orientation. Then, the recording sheet is caused again to pass through the passage between the intermediate transfer belt  13  and the secondary image transfer unit  25  to receive a composite color image on the back surface thereof. After that, the recording sheet with the front and back sides printed passes through the ejection passage selected by the switch pawl  55  and is ejected to the output tray  27  by the pair of sheet ejection rollers  26 . 
   After the image transfer, the intermediate transfer belt  13  further moves to undergo a cleaning of unused toner particles by the cleaning unit  18  and to become ready for a next image transfer process. 
     FIG. 2  shows a major portion of the color copying engine  100  in the color copying apparatus  1 . As indicated in  FIG. 2 , in the tandem mechanism  10 , the four image forming units  11  for the colors of Y, M, C, and Bk are arranged in this order in the exemplary embodiment from an upstream side to a downstream side in a moving direction of the intermediate transfer belt  13  in a horizontal area between the rollers  14  and  15  where the four image forming units  11  contact the intermediate transfer belt  13 . With this order, a “first copy time” of a copying operation in black can be shortened by a time period corresponding to a length from the most upstream photosensitive drum  12  for the color Y to the most downstream photosensitive drum  12  for the color Bk. 
     FIG. 3  enlarges the image forming units  11  for the colors of C and Bk, for example, as a portion of the tandem mechanism  10 . As shown in  FIG. 3 , in the image forming unit  11  for the color of C, for example, the photosensitive drum  12  is surrounded by a charging unit  56 , a development unit  60 , the secondary image transfer unit  17 , a cleaning unit  58 , and a discharging unit  59 . A laser light beam L runs to the photosensitive drum  12  between the charging unit  56  and the development unit  60 . 
     FIG. 4  shows a toner replenishing mechanism for replenishing the development unit  60  of the image forming unit  11  with toner. In  FIG. 4 , a toner container  80  contains toner which is transferred to the development unit  60 . This toner container  80  is enclosed by an enclosure  110  (see  FIG. 8 ) of the color copying engine  100 . The enclosure  110  is provided with a nozzle  90  which is inserted into the toner container  80 . When the toner container  80  is exchanged and a new one is inserted downwardly into the enclosure  110 , the nozzle  90  is inserted upwardly into the new toner container  80 . The nozzle  90  has a tubular structure and is provided with an upper end  91  in a cone-like shape having a pointed top. The upper end  91  is integrated with the nozzle  90  or is adhered to the nozzle  90 . The nozzle  90  is provided with an opening  92  for exchanging air and taking in the toner at a position below the upper end  91 . The nozzle  90  includes a passage  93  connected to the opening  92  and which is provided with a connection end  94  for connecting a toner transportation tube  85  for transporting toner therethrough. The passage  93  is also provided with an air inlet  95  at a position above the connection end  94 . 
   In this embodiment, an air pump  96  is connected to the air inlet  95  with an air transportation pipe  97 . When the air pump  96  is in operation, it discharges the air in a confined jet to inside the toner container  80  from the bottom via the air transportation pipe  97  and the passage  93 . The jet air entered inside the toner container  80  agitates the toner and fluidizes the toner in the toner container  80 . 
   The toner container  80  includes an external case  81  serving as a protection cover and a toner sack  82  stored inside the external case  81 . The toner sack  82  is flexible and exchangeable. The external case  81  is made of a rigid paper material such as a corrugated cardboard or a plastic material, for example, and has an internal space for storing the toner sack  82 . The thus-structured toner container  80  is an easy-to-handle container since the flexible toner sack  82  is protected from an external impact with the external case  81 . 
   The toner sack  82  is made of at least one flexible sheet material such as a polyester film, a polyethylene film, or the like having a thickness of the order of from about 80 μm to 125 μm. The toner sack  82  has an opening with a ring-shaped portion  83  at a bottom center thereof for discharging the toner. The ring-shaped portion  83  is made of plastic such as polyethylene, nylon, or the like. The opening with the ring-shaped portion  83  is provided with a seal  84  serving as a self-closing valve. The seal  84  includes at least one layer of seal and is made of an elastic material including a sponge foam or the like. The toner sack  82  has a tapered width decreasing as close to the opening with the ring-shaped portion  83  so that the toner cannot remain inside the toner sack  82 . 
   With the thus-structured toner container  80 , when the toner container  80  is inserted downwardly into the enclosure  110 , the nozzle  90  is inserted upwardly into the toner container  80 . 
   A mechanical shutter may be provided to the toner container  80  to automatically close the opening with the ring-shaped portion of the toner sack  82  when the toner sack  82  is removed from the toner container  80 . 
   As shown in  FIG. 4 , the development unit  60  is provided with a sub-hopper  61  on the top thereof. The toner discharged from the toner container  80  is temporarily stored in the sub-hopper  61 . The sub-hopper  61  is provided with a powder pump  70  on the top thereof. The powder pump  70  transports the toner discharged from the toner container  80  to the sub-hopper  61 . The powder pump  70  is a pump having a single eccentric screw. The powder pump  70  includes a rotor  71 , a stator  72 , and a holder  73 . The rotor  71  is made of rigid metal and formed in an eccentric screw shape. The stator  72  is made of elastic material such as a rubber and internally has spiral grooves in a two-screw shape. The holder  73  stores the rotor  71  and the stator  72 , and is made of the plastic material same as that used for the passage for transporting the toner. The rotor  71  is stored inside the stator  72  and is connected with a driving gear  74  using a pin connector so that the rotor  71  can be driven for rotation by the driving gear  74  and, as a result, the toner inside the stator  72  is transported to the sub-hopper  61  by an action of a negative pressure generated by the rotation of the rotor  71  in the powder pump  70 . A gear  75  (see  FIG. 5 ) integrally formed with the driving gear  74  is connected with a first clutch  76  via an idle gear (not shown). By switching the first clutch  76  between connection and disconnection, the operation of the powder pump  70  is controlled. The first clutch  76  and a second clutch  68  (later explained) are provided to a rotation driving shaft  79 , as shown in  FIG. 5 , which is driven by a driving mechanism (not shown). 
   The holder  73  includes a toner sucking portion  77  at an end thereof, a right end of the holder  73  in  FIG. 4 , to which the above-mentioned toner transportation tube  85  is connected. The toner transportation tube  85  preferably is a flexible tube having a diameter of from about 4 mm to 10 mm, for example, and is made of a rubber material having a superior anti-toner characteristic, such as polyurethane, nitrile, EPDM (ethylene-propylene-diene-methylene), silicon, or the like. Such toner transportation tube  85  can be bent easily and arbitrarily in any direction. 
   When the toner discharging portion of the toner container  80  is positioned lower than a toner receiving portion of the sub-hopper  61  in the vertical direction, the toner can smoothly be transported from the toner container by using the above-mentioned powder pump  70 . 
   The sub-hopper  61  is divided into an upper chamber  62  and a lower chamber  63 . As shown in  FIGS. 6 and 7 , where  FIG. 6  is a top view of the upper chamber  62  and  FIG. 7  is a top view of the lower chamber  63 , the upper chamber  62  has a larger floor area than the lower chamber  63  and is provided with a pair of upper screws  64  and  65  and a partition  166  having two cut ends, left and right cut ends in  FIG. 6 , where the partition  166  is positioned between the pair of upper screws  64  and  65  and the two cut ends are shorter than an internal width of the upper chamber  62 . In  FIG. 6 , a position A in the upper chamber  62  indicated by a circular mark with a partly-dotted line is a position to which the toner transported by the powder pump  70  is supplied. The toner supplied at the position A is transported within the upper chamber  62  in a direction P 1  by the rotations of the upper screws  64  and  65 . An opening B in the upper chamber  62  indicated by a square mark with a solid line is an opening connecting inside spaces of the upper chamber  62  and the lower chamber  63 . That is, the toner moved along in the direction P 1  by the upper screws  64  and  65  is transferred to a region around the connecting opening B and drops down to an inside floor of the lower chamber  63  by its weight through the opening B. 
   As shown in  FIG. 7 , the lower chamber  63  is provided with a lower screw  66 . A position B′ in the lower chamber  63  indicated by a square mark with a solid line is a position to which the toner falls from the upper chamber  62 . The toner received at the position B′ is transported within the lower chamber  63  in a direction P 2  by the rotation of the lower screw  66 . An opening C in the lower chamber  63  indicated by a square mark with a solid line is a toner replenishing opening connecting inside spaces of the lower chamber  63  and the development unit  60 . That is, the toner moved along in the direction P 2  by the lower screw  66  is transferred to a region around the opening C and drops down to an inside floor of the lower chamber  63  by its weight through the opening C. 
   The sub-hopper  61  is thus structured so that the toner transported by the powder pump  70  is temporarily stored and is transferred to the development unit  60  by the upper screws  64  and  65  and the lower screw  66 . That is, these upper screws  64  and  65  and the lower screw  66  serve as a toner transportation mechanism in the sub-hopper  61 . In addition, as shown in  FIG. 5 , the upper screws  64  and  65  and the lower screw  66  are provided with gears  64   a,    65   a,  and  66   a,  respectively, which are connected via a group of idle gears  67  with a second clutch  68  provided to the driving shaft  79  so that the operations of the upper screws  64  and  65  and the lower screw  66  are controlled by the second clutch  68  which turns on and off. 
   Further, the sub-hopper  61  is provided with a toner sensor  69  for detecting the toner in the upper chamber  62  when an amount of toner exceeds a predetermined value. The toner sensor  69  is located at a position on a wall near the position A of the upper chamber  62 . The toner sensor  69  is a vibration type sensor having a detection surface  69   a , as shown in  FIG. 6 , for detecting the toner in the upper chamber  62  when an amount of toner exceeds the predetermined value. 
   The thus-structured toner replenishing mechanism starts its operation upon a receipt of an instruction signal for replenishing the toner to the development unit  60  from a toner density sensor (not shown), for example. In the toner replenishing operation, the second clutch  68  is turned on to drive the upper screws  64  and  65  and the lower screw  66  so as to supply the toner to the development unit  60  by an amount according to a length of time that the screws are driven. At the same time, the toner sensor  69  monitors the toner amount in the sub-hopper  61 . Upon a detection by the toner sensor  69  that the toner amount decreases under a predetermined amount, the powder pump  70  is activated to transport the toner of the toner container  80  to the sub-hopper  61 . This process can be performed without the needs of a high accuracy in controlling the amount of the toner replenishment to the sup-hopper  61 . Accordingly, the amount of toner to be transported by the powder pump  70  is determined to be greater than an amount of toner to be transferred from the sub-hopper  61  to the development unit  60  by the upper and lower screws. 
   In addition, if the toner amount detected by the toner sensor  69  maintains under the predetermined amount even with plural times of the toner replenishing operation by the powder pump  70 , the toner container  80  is judged as nearly empty, which is referred to as a toner near-end status. When the toner near-end status is detected, a caution for an exchange of the toner container  80  is displayed on an indication member (not shown), for example, of the operation panel  120 . When the toner container  80  is not exchanged despite the above-mentioned display of the caution, the image forming operation is prohibited after the execution of the image forming operation a predetermined number of times. 
   Since the color copying apparatus  1  uses the powder pump  70  to replenish the development unit  60  with the toner of the toner container  80 , the placement of the enclosure  110  for the toner container  80  is highly flexible. The enclosure  110 , however, is not preferably placed at a lower part of the color copying engine  100  since a user may need to bow in exchanging the toner container  80 . A top and front part of the color copying engine  100  is a preferable part for the enclosure  110  to be placed. In addition, if the toner container  80  has an insufficient toner capacity, a frequent exchange of the toner container  80  may be required and therefore the toner container  80  preferably has a sufficient capacity of toner. 
     FIG. 8  shows the enclosure  110  for the toner container  80  which is placed at a position satisfying the above-mentioned requirements. In the exemplary embodiment, the position is located in an upper front part of the color copying engine  100  and underneath the operation panel  120 . At this position, however, the insertion of the toner container into the enclosure  110  is obstructed by the operation panel  120 . 
   In the color copying apparatus  1 , the toner container  80  is configured to tilt away from the color copying engine  100 , as shown in  FIG. 8 , so that the toner container  80  can be removed, in a direction of arrow P 3 , and inserted into the enclosure  110  with being obstructed by the operation panel  120 . More specifically, behind the enclosure  110 , there is provided a housing plate  130  which encloses a unit of the image forming mechanism including the development unit  60  and the toner replenishing mechanism including the powder pump  70 . The enclosure  110  includes a holder  121  for holding the toner container  80 . At a lower part of the holder  121 , the nozzle  90  is mounted vertically. The holder  121  is held on the housing plate  130  for rotation about a rotation shaft  131 , as shown in  FIG. 8 , so that the enclosure  110  can be moved to a closed position at which the enclosure  110  is fit underneath the operation panel  120 , where the toner container  80  and associated components are illustrated with dotted lines, and a tilt position at which the toner container  80  can be exchanged without being obstructed by the operation panel  120 , where the toner container  80  and the holder  121  are illustrated with two-dotted-chain lines. The rotation shaft  131  is provided to a position close to the housing plate  130  and in a lower part of the toner container  80 . 
   In addition, the enclosure  110  is provided with a stopper (not shown) for engaging the enclosure  110  at the closed position and a release button  111  for releasing the engagement of the enclosure  110  at the closed position by the stopper. When the release button  111  is depressed relative to the enclosure  110  staying at the close position, the stopper is released and the enclosure  110  is tilted towards the tilt position by its own weight. Then, the enclosure  110  settles at the tilt position. After an exchange of the toner container  80 , the enclosure  110  can be lifted by manually to the closed position. When the enclosure  110  comes to the closed position, the stopper automatically engages the enclosure  110  at the closed position. The stopper may include a tapered pawl with spring effect for allowing the enclosure  110  to move from the tilt position to the closed position. 
   Since the enclosure  110  is opposed to the powder pump  70  and the sub-hopper  61  relative to the housing plate  130 , the toner transportation tube  85  has a sufficient length to be flexibly bent and is arranged to pass through a hole (not shown) provided to the housing plate  130  so as to connect the nozzle  90  with the powder pump  70 . When the enclosure  110  moves between the close position and the tilt position, the toner transportation tube  85  follows the movement as it is flexible. Therefore, the toner transportation tube  85  may not cause a problem such as a breakage, a pull-out, and so forth. If the toner transportation tube  85  is excessively long, however, it may be caught on by other components causing damage during a assembly of the mechanism or exchanging the toner container  80 . Therefore, it is preferable to arrange the hole of the housing plate  130  for allowing the toner transportation tube  85  to pass through at a position close to the rotation shaft  131  so that the movement of the toner transportation tube  85  is minimal. 
   When the toner transportation tube  85  is made of a single tube, it may be damaged by rubbing between an inner circumferential surface and an outer circumferential surface. To avoid this problem, it is preferable that the toner transportation tube  85  is made of plural tubes, as shown in  FIG. 9 . That is, a connection pipe  132  is provided to the hole of the housing plate  130 , and first and second tubes  85   a  and  85   b  are provided. The first tube  85   a  connects between the nozzle  90  and the connection pipe  132 , and the second tube  85   b  connects between the connection pipe  132  and the powder pump  70 . In this case, the first tube  85   a  is caused to move as the enclosure  110  is moved but the second tube  85   b  is not caused to move since the powder pump  70  is not moved. Therefore, the first tube  85   a  is preferably made of a flexible material to follow the movement of the enclosure  110  and the second tube  85   b  is preferably made of a relatively rigid material to avoid breakage. 
     FIG. 10  shows an exemplary structure of the enclosure  110 , where the holder  121  of the enclosure  110  is divided into first and second holders  121   a  and  121   b.  The first holder  121   a  holds the toner container  80  for the color of Bk, and the second holder  121   b  holds the toner containers  80  for the colors of Y, C, and M. As an alternative, it is possible to hold the toner containers  80  for the colors of Y, C, M, and Bk with a single holder, or four individual holders. 
   In addition, it is possible to install the enclosure  110  with the toner containers  80  therein inside an entire front cover of the color copying apparatus  1  for covering the inside mechanism such as the image forming mechanism, or a partial front cover prepared specifically for the enclosure  110 . In the former case, the image forming operation is prohibited when the entire front cover is open to exchange the toner container  80 , but in the latter case, the image forming operation is not necessarily prohibited when the partial front cover for the enclosure  110  is open to exchange the toner container  80 . 
   When the above-mentioned partial front cover is applied to the color copying apparatus  1 , the image forming operation can be executed under the conditions that the toner container  80  is in the toner near-end status, because the color copying apparatus  1  has the sub-hopper  61  and can still supply the requisite toner to the image forming operation. Accordingly, the color copying apparatus  1  does not need to stop the image forming operation and can continue the operation even when the toner near-end is detected. When the toner near-end is detected, the color copying apparatus  1  displays an instruction for exchanging the toner container  80  on the operation panel  120 . The enclosure  110  may then be tilted to the tilt position to exchange the toner container  80 . Upon the exchange of the toner container  80 , the transportation of toner from the toner container  80  can be started by the powder pump  70  even with the enclosure  110  at the tilt position. Thus, the color copying apparatus  1  can continue the image forming operation even when the toner near-end is detected. 
   Further, it becomes possible for the color copying apparatus  1  to check whether the toner container  80  is correctly set to the holder  121  of the enclosure  110  when it is exchanged, by using the above-described feature of the color copying apparatus  1 . That is, since the transportation of toner from the toner container  80  can be started by the powder pump  70  while the enclosure  110  stays at the tilt position, the color copying apparatus  1  can initiates the toner transportation and monitors the result of the toner transportation during the time the enclosure  110  stays at the tilt position after the tone container  80  is exchanged, thereby detecting an inappropriate setting of the toner container  80 . 
     FIG. 11  shows a toner replenishing mechanism for replenishing the development unit  60  of an image forming unit  18  with toner. The image forming unit  18  utilizes a toner transportation apparatus with a screw pump mechanism. In  FIG. 11 , a toner container  80  contains toner which is transferred to the development unit  60 . This toner container  80  is enclosed by an enclosure  99  ( FIG. 16 ) of the color copying engine  100 . The enclosure  99  appears when a front door  100   a  ( FIG. 20 ) of the color copying engine  100  is opened and is provided with a nozzle  110  forming a part of the toner replenishing mechanism. When the toner container  80  is placed into the enclosure  99 , the nozzle  110  is inserted into the toner container  80 . The nozzle  110  has a passage  110   a  therein. The passage  110   a  is connected to one end of the nozzle to communicate with a toner transportation tube  78  for transporting toner therethrough. 
   The toner container  80  includes a toner sack  81  which is flexible and exchangeable. The toner sack  81  is made of at least one flexible sheet material such as a polyester film, a polyethylene film, or the like having a thickness of the order of from 80 μm to 200 μm. The toner sack  81  has an opening with a single toner discharging unit  183  at a bottom center thereof for discharging the toner. The toner sack  81  also has a tapered width decreasing as close to the opening with the toner discharging unit  183  so that the toner cannot remain inside the toner sack  81 . 
   As shown in  FIG. 12 , the toner container  80  includes the toner sack  81  and the toner discharging unit  183 . The flexible toner sack  81  includes two sheets  81   a  and  81   b  for the front and back sides, two sheets of  81   c  and  81   d  for right and left sides, and an upper sheet  81   e  attached together. The right and left side sheets  81   c  and  81   d  have folds  81   f  to inwardly fold sidewalls of the container. When the container is filled with toner, the folds  81   f  expand to be in a container shape. When the container has no toner, it is folded along the folds  81   f  to contact or closely position the front and back side sheets  81   a  and  81   b  each other. 
   As shown in  FIGS. 13 to 15 , the toner discharging unit  183  includes an upper main body  84  and an lower main body  85 . The upper main body  84  is provided with a container fixing unit  88  which welds the toner sack  81  configured like a boat seen from the top. The lower main body  85  is of generally substantially rectangular shape. In the lower main body  85 , when the left side as shown in  FIG. 21  is the front side, the lower main body  85  of the toner discharging unit  183  has a front and back side width Wa wider than both side width Wb. The toner discharging unit  183  is made of resin such as polyethylene, nylon, or the like. The upper main body  84  is formed integral with the lower main body  85 . 
   The toner discharging unit  183  includes two holes for discharging toner therethrough. One is an internal hole  86  of the toner sack  81 . The other is a shutter hole  87  for communicating with the internal hole  86  and removalby inserting a shutter which is described later. The hole  86  is a longitudinal hole extending in a vertical direction with the toner discharging unit  183  facing downward. The shutter hole  87  is a transverse hole with an axis line generally perpendicular to an axis line of the internal hole  86 . In this example, the shutter hole  87  is a penetrating hole of a circular cross-section through the front side of the lower main body  85  to the back side. The internal hole  86  is a circular cross-sectional hole having the shorter length in diameter inside a boat-shaped container fixing unit  88  with a funnel-shaped constraint  86   a  formed therebetween. That is, the internal hole  86  becomes small by the constraint  86   a  as it approaches the shutter hole  87  to communicate with an upper portion of the shutter hole  87 . Therefore, the internal hole  86  has a smaller aperture than the shutter hole  87  in the communication between the internal hole  86  and the shutter hole  87 . When a shutter  92  is inserted in the shutter hole  87 , the hole for discharging the toner is securely closed. 
   In this embodiment, the shutter  92  has an axially circular cross-section with a slightly smaller diameter than the shutter hole  87 . This allows the shutter  92  to be securely inserted in the shutter hole  87 . However, when the shutter  92  has a smaller diameter than the shutter hole  87 , toner and air are leaked between the shutter  92  and the shutter hole  87 . The toner leakage causes toner contamination while the air leakage causes the toner container  80  to be reduced in volume. In order to avoid such a problem, O-rings  89  are provided with the toner discharging unit  183  to seal between the shutter hole  87  and the shutter  92 . Since the shutter hole  87  is a penetrating hole, the O-rings  89  are provided on both sides of the shutter hole  87 . Moreover, providing the O-rings  89  on both sides of the shutter hole  87  require grooves for attachment with adhesion or the like, causing labor intensive for securing the O-rings  89  and a high assembly cost. 
   Accordingly, the toner discharging unit  183  according to an embodiment shown in  FIGS. 13 to 15  is divided into an inner component  195  and an outer component  91 , both components supporting the O-rings  89 . Specifically, the inner component  195  has an engagement groove  93  for engaging the O-rings  89 . The outer component  91  is provided with an attachment  94  for attaching the inner component  195 , the container fixing unit  88 , a retainer  95  for retaining the O-rings  89  engaged by the engagement groove  93 . When the O-rings  89  are engaged within the engagement groove  93  to attach the inner component  195  to the outer component  91 , they are retained by the retainer  95  to thereby prevent the O-rings  89  from slipping out. 
   The shutter hole  87  is provided across the inner component  195  and the outer component  91  to attach the inner component  195  to the attachment  94  of the outer component  91  and to insert the shutter  92  into the shutter hole  87  so that the inner component  195  is assembled into the outer component  91 . Further, easy operation of extracting the shutter  92  enables the toner discharging unit  183  to be divided into the inner component  195  and the outer component  91 . Therefore, when the shutter  92  is moved widely or extracted with toner container  80  filled with toner, toner is prone to overflow from it so that the shutter  92  provides a diameter of 8 mm at maximum, preferably, 6 mm to avoid moving the shutter  92  with a finger. That is, when the shutter  92  has a diameter of 10 mm, toner frequently leaks with a finger moving the shutter  92  so that the shutter  92  is set within a 8 mm diameter. 
   On the other hand, as shown in  FIGS. 9 and 11 , the development unit  60  for replenishing toner is provided with a sub-hopper  61  for storing toner on the top thereof. The toner discharged from the toner container  80  is temporarily stored in the sub-hopper  61 . The sub-hopper  61  is provided with a powder pump  70  on the top thereof. The powder pump  70  transports the toner discharged from the toner container  80  to the sub-hopper  61 . The powder pump  70  is a pump having a single eccentric screw. The powder pump  70  includes a rotor  71 , a stator  72 , and a holder  73 . The rotor  71  is made of rigid metal and formed in an eccentric screw shape. The stator  72  is made of elastic material such as a rubber and internally has spiral grooves in a two-screw shape. The holder  73  stores the rotor  71  and the stator  72 , and is made of the plastic material same as that used for the passage for transporting the toner. The rotor  71  is stored inside the stator  72  and is connected with a driving gear  74  using a pin connector so that the rotor  71  can be driven for rotation by the driving gear  74  and, as a result, the toner inside the stator  72  is transported to the sub-hopper  61  by an action of a negative pressure generated by the rotation of the rotor  71  in the powder pump  70 . A gear  75  (see  FIG. 9 ) integrally formed with the driving gear  74  is connected with a first clutch  76  via an idle gear (not shown). By switching the first clutch  76  between connection and disconnection, the operation of the powder pump  70  is controlled. The first clutch  76  and a second clutch  68  (later explained) are provided to a rotation driving shaft  79 , which is driven by a driving mechanism (not shown). 
   The holder  73  includes a toner sucking portion  77  at an end thereof, a right end of the holder  73  in  FIG. 11 , to which the above-mentioned toner transportation tube  78  is connected. The toner transportation tube  78  preferably is a flexible tube having a diameter of from 4 mm to 10 mm, for example, and is made of a rubber material having a superior anti-toner characteristic, such as polyurethane, nitrile, EPDM (ethylene-propylene-diene-methylene), silicon, or the like. Such toner transportation tube  78  can be bent easily and arbitrarily in any direction. 
     FIG. 10  is a top view of the upper chamber  62  and  FIG. 11  is a tope view of the lower chamber  63 . The sub-hopper  61  is divided into an upper chamber  62  and a lower chamber  63 . The upper chamber  62  has a larger floor area than the lower chamber  63  and is provided with a pair of upper screws  64  and  65  and a partition  66  having two cut ends, left and right cut ends in  FIG. 10 , where the partition  66  is positioned between the pair of upper screws  64  and  65  and the two cut ends are shorter than an internal width of the upper chamber  62 . In  FIG. 10 , a position A in the upper chamber  62  indicated by a circular mark with a partly-dotted line is a position to which the toner transported by the powder pump  70  is supplied. The toner supplied at the position A is transported within the upper chamber  62  in a direction P 1  by the rotations of the upper screws  64  and  65 . An opening B in the upper chamber  62  indicated by a square mark with a solid line is an opening connecting inside spaces of the upper chamber  62  and the lower chamber  63 . 
   As shown in  FIG. 16 , the image forming apparatus includes the enclosure  99  to which the toner container  80  having four toner folders for four colors is attached. The enclosure  99  with four folders has a substantially identical internal structure for each folder except that one folder having the toner container  80  for black is widen. 
   As shown in  FIGS. 17 and 18 , the enclosure  99  includes an open and close folder  103  which has the separated toner container  80  for each color and is attached to a body frame  101  with a rotation shaft  102 . The open and close folder  103  is pivotally mounted with respect to the body frame  101  between a closed position shown in  FIG. 18  and a tilt position shown in  FIG. 19 . The open and close folder  103  is provided with a pair of nozzle guide members (not shown) and a guide tube  105  at the bottom thereof. The nozzle guide members slideably support a nozzle  110 . The guide tube  105  is slideably engaged with a slider  106  for returning the inserted nozzle  110 . The open and close folder  103  is provided with a fixed cover  115  on an outside surface thereof. Further, the open and close folder  103  has an open and close handle  125  on the top thereof movably mounted in the vertical direction. The open and close handle  125  includes a stopper  121  for engaging the open and close folder  103  at the closed position when the open and close folder  103  can be lifted by manually to the closed position. The handle  125  is made of resin and integrally forms a resilient arm  122  at the bottom thereof. The resilient arm  122  lifts the handle  125  to its uppermost position at all times. The nozzle  110  is of the same diameter as the shutter  92 . 
   The nozzle  110  is provided with a slide arm  111  integrally formed at both sides thereof, the slide arm  111  being movably mounted to the nozzle guide members. The slide arm  111  includes a pawl  112  on an end thereof and the pawl  112  is engaged with an end of the nozzle guide members, thus preventing the nozzle  110  from pulling out of the folder  103 . Arranged between the nozzle  110  and the folder  103  is an compression spring  113  which fits loosely to wrap around the nozzle  110 . The spring  113  holds the nozzle  110  with spring effect at a position where the pawl  112  is engaged with an end of the nozzle guide members at all times. 
   The guide tube  105  expands axially toward the nozzle  110  to form a hole  105   a  into which the shutter  92  can be inserted at one end opposite the nozzle  110 . The other end of the nozzle  110  is sealed by the fixed cover  115 . The guide tube  105  encloses the slider  106  and a compression spring  107 , the compression spring  107  pushing the slider  106  to the nozzle  110 . The slider  106  has a cross section in a convex form and is held in the guide tube  105  even when the slider  106  is pushed to the compression spring  107  by a detent  108  which is formed at the nozzle side of the guide tube  105 . The open and close folder  103  is provided with a guide frame  109  for placing the inserted toner container  80  in the set position. The guide frame  109  has a bottom portion where the nozzle  110  is provided so as to form a holder for holding a bottom body  85  of a toner discharging unit  183  of the toner container  80 . The holder includes an opening (not shown) through which the nozzle  110  and the shutter  92  pass. 
   When the thus-structured enclosure  99  is pulled out with the handle  125  positioning downward, the stopper  121  disengages from an engagement groove  123  of the body frame  101  to pivot the open and close folder  103  about the rotation shaft  102  to the position where the bottom of the folder  103  contacts with the frame  101  as shown in  FIG. 19 . The folder  103  then moves to a tilt position, where the nozzle  110  is retracted inward as shown on the left hand side of  FIG. 18 . At this position, the toner container  80  is pushed with the toner discharging unit  183  downward so that the shutter  92  of the toner discharging unit  183  is lowered to a position opposed to the nozzle  110  which is held at the position where the pawl  112  contacts with the nozzle guide members by the compression spring  113 . 
   After the toner container  80  is inserted in a predetermined position, the open and close folder  103  is returned to a closed position shown in  FIG. 18 . This operation causes the nozzle  110  to be inserted in the shutter hole  87  and the shutter  92  moves from the hole  105   a  to the guide tube  105 . The nozzle  110  includes a toner inlet  114  on a circumference surface near its end. The toner inlet  114  communicates with the lower portion of an inner hole  33  provided to the toner discharging unit  183  so that a path for transporting the toner from the toner container  80  to the development mechanism  60  is opened. The shutter  92  pushed toward the guide tube  105  by an insertion of the nozzle  110  is hold in a position across the shutter hole  87  and the guide tube  105  without completely pulling out of the shutter hole  87 . 
   When the nozzle  110  is inserted into the shutter hole  87 , the compression spring  113  is compressed against the open and close folder  103 . Further, the compression spring  107  provided in the guide tube  105  is also compressed by the insertion of the shutter  92  through the slider  106 . Thus, when the folder  103  is moved from the closed position to the tilt position, the nozzle  110  returns to its original position with a force of the compression spring  113  and the shutter  92  also returns to its original position with a force of the compression spring  107 . Therefore, the nozzle  110  pulls out of the shutter hole  87  of the toner container  80  and then the shutter  92  is again inserted into the shutter hole  87 . 
   As previously described, by simply setting the toner container  80  to the color copying apparatus  1 , the container  80  communicates with a toner replenishment path. When the open and close folder  103  is opened, the nozzle  110  pulls out of the shutter hole  87  and then the shutter  92  immediately returns so that a toner does not leak from the toner container  80 . In this embodiment, since the nozzle  110  and the slider  106  move by the same amount toward the same direction at the time of a setup of the toner container  80 , the nozzle  110  and the slider  106  may be integrated as shown in  FIG. 20 . This structure eliminates the problems such that the slier  106  does not move even if the nozzle  110  pulls out and the shutter  92  does not seal the shutter hole  87 . 
     FIGS. 21 and 22  show another example of an enclosure. In this example, the open and close folder  103  slideably moves in the directions of arrows by a linear guide  130  so that the folder  103  is slideably opened and closed to the color copying apparatus  1 . 
   The open and close folder  103  is attached to the apparatus  1  via the linear guide  130 . As shown in  FIG. 22 , at the same time that the folder  103  is drawn from the apparatus  1 , the nozzle  110  moves away from the toner discharging unit  183  so that the toner container  80  can be removed. At this time, when the container  80  is replaced with new one and the open and close folder  103  is inserted into the apparatus  1 , the nozzle  110  is set into the toner discharging unit  183  to replenish toner into the development mechanism. 
     FIG. 23  shows another example of an enclosure. In this example, the open and close folder  103  is immovable relative to the color copying apparatus  1 . In addition, to insert and remove the toner container  80 , a door  140  is provided on the folder  103 . A nozzle support member  116  for supporting the nozzle  110  is supported by the liner guide (not shown) in the directions of arrows to permit horizontal movement. The nozzle support member  116  is moved in the directions of the arrows by a cam  141  which pivots around a fulcurum  142 . The door  140  pivots around a fulcurum  143 . 
   Configured in this manner, the cam  141  connects the door  140  by an arm  144  as shown in  FIG. 23 . so that the cam  141  rotates in combination with an open and close of the door  140  to insert and remove the nozzle  110 . Therefore, opening the door  140  moves the nozzle  110  away from the toner discharging unit  183  to allow for a replacement and removal of the toner container  80 . Closing the door  140  inserts the nozzle  110  into the toner discharging unit  183  via the arm  144 , the cam  141  and the nozzle supporting member  116  to allow for toner absorption and replenishment. 
   Referring now to  FIG. 24 , another example of a toner replenishing mechanism will be described. In  FIG. 24 , a toner replenishing mechanism utilizes the powder pump  70 , which is similar to the embodiment described above, located to near the development unit  60  as a screw pump mechanism. The enclosure  99  of an image forming apparatus body is provided with a nozzle  190  which is inserted into the toner sack  81 . The nozzle  190  has a circular cross section. The toner container  80  is inserted upwardly into the enclosure of the apparatus body to insert the nozzle  190  into a toner discharging unit. The nozzle  190  of the enclosure includes a tubular structure having a passage  191  which is connected to a toner transportation tube  178  at the end thereof. The passage  191  is bent to the right of the drawing above the toner transportation tube  178  to connect to an air pump  194  via an air transportation tube  193 . 
   When the air pump  194  is in operation, it discharges the air in a confined jet to inside the toner container  80  from the bottom via the air transportation pipe  193 . The jet air entered inside the toner container  80  agitates the toner and fluidizes the toner in the toner container  80 . When the powder pump  70  is in operation, it absorbs the toner and the air in the toner container  80  to replenish the toner into the development unit  60 . 
   Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.

Technology Classification (CPC): 6