Patent Publication Number: US-9897971-B2

Title: Powder collecting device and processing apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-135234 filed Jul. 7, 2016 and No. 2016-220896 filed Nov. 11, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a powder collecting device and a processing apparatus including the powder collecting device. 
     SUMMARY 
     According to an aspect of the invention, there is provided a powder collecting device including a collecting container and a ventilation passage. The collecting container is removably attachable to a housing of a processing apparatus including a powder processing unit, has one or more collecting openings through which heat-melting powder transported from the powder processing unit is collected, and includes an accommodation space capable of accommodating the collected powder. The ventilation passage is partitioned from the accommodation space of the collecting container. Airflow generated by an airflow generator passes through the ventilation passage. The ventilation passage extends in a longitudinal direction of the collecting container, and has an inlet through which the airflow is introduced and a ventilation hole formed in a downstream section of the ventilation passage in a direction of the airflow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1A  is a schematic plan view illustrating a processing apparatus according to an exemplary embodiment of the present invention is applied; 
         FIG. 1B  illustrates the processing apparatus viewed in the direction of arrow IB in  FIG. 1A ; 
         FIG. 1C  illustrates the processing apparatus viewed in the direction of arrow IC in  FIG. 1A ; 
         FIG. 2  illustrates the overall structure of an image forming apparatus, which is a processing apparatus according to Exemplary Embodiment 1; 
         FIG. 3  illustrates the image forming apparatus according to Exemplary Embodiment 1 viewed from the user (from the front); 
         FIG. 4  illustrates a part of a developer-collecting system illustrated in  FIG. 3 ; 
         FIG. 5  illustrates the part illustrated in  FIG. 4  from which a developer-transporting unit is removed; 
         FIG. 6  illustrates the flow of developer in the developer-collecting system illustrated in  FIG. 3 ; 
         FIG. 7  illustrates the internal structure of the developer-transporting unit illustrated in  FIG. 3 ; 
         FIG. 8  illustrates an example of a ventilation structure for the developer-transporting unit according to Exemplary Embodiment 1; 
         FIG. 9  illustrates the developer-transporting unit illustrated in  FIG. 8  from which a ventilation duct is removed; 
         FIG. 10  illustrates the ventilation duct illustrated in  FIG. 9  viewed in the direction of arrow X; 
         FIG. 11  illustrates the location of the ventilation duct in the image forming apparatus according to Exemplary Embodiment 1; 
         FIG. 12  illustrates a part of  FIG. 11 ; 
         FIG. 13  illustrates the developer-transporting unit illustrated in  FIG. 8  viewed in the direction of arrow XIII; 
         FIG. 14  illustrates the positional relationship between ventilation holes in the ventilation duct and image forming units according to Exemplary Embodiment 1; and 
         FIG. 15  illustrates airflow through the ventilation duct according to Exemplary Embodiment 1. 
     
    
    
     DETAILED DESCRIPTION 
     Summary of Exemplary Embodiment 
     In an exemplary embodiment, as illustrated in  FIG. 1A , a processing apparatus  10  that uses powder includes one or more powder processing units  12  (powder processing units  12   a  to  12   d  in this example) that are disposed in a housing  11  and that perform a process by using the powder, and a powder collecting device  1  that collects the powder transported from the powder processing units  12 . 
     The processing apparatus  10  may be any appropriate type of processing apparatus as long as the processing apparatus  10  includes the powder processing units  12  that perform a process by using powder (for example, imaging units that visualize electrostatic latent images by using developer as the powder). 
     In particular, in the present exemplary embodiment, as illustrated in  FIGS. 1A to 1C , a powder collecting device  1  includes a collecting container  2  and a ventilation passage  5 . The collecting container  2  is removably attachable to a front section of the housing  11  of the processing apparatus  10  including the powder processing units  12 . The collecting container  2  has one or more collecting openings  3  through which heat-melting powder transported from the powder processing units  12  is collected, and includes an accommodation space capable of accommodating the collected powder. The ventilation passage  5  is partitioned from the accommodation space of the collecting container  2 . Airflow Af generated by an airflow generator  13  passes through the ventilation passage  5 . The ventilation passage  5  extends in a longitudinal direction of the collecting container  2 , and has an inlet  6  through which the airflow Af is introduced and a ventilation hole  7  formed in a downstream section of the ventilation passage  5  in a direction of the airflow Af. 
     In the above-described technical feature, the collecting container  2  may be any type of collecting container that has one or more collecting openings  3  and that is removably attachable to a front section of the housing  11  at a predetermined location. The collecting container  2  may be removably attached by retaining the collecting container  2  at a predetermined installation position in such a manner that the collecting container  2  is extractable along a guide or pivotable about a bottom portion thereof. 
     The collecting container  2  is not limited as long as it collects the heat-melting powder (for example, imaging powder such as toner) transported from the powder processing units  12 . The collecting container  2  may be configured to either store the collected powder or transport the collected powder to another collecting container. 
     The ventilation passage  5  is not limited as long as it is partitioned from the accommodation space of the collecting container  2 . The ventilation passage  5  may be provided on either an exterior wall or an interior wall of the collecting container  2 . The ventilation passage  5  may be either integrated with the collecting container  2  or formed separately from the collecting container  2 . The member that defines the ventilation passage  5  is required to allow the airflow Af to pass through the ventilation passage  5 . The inlet  6  may be provided so that the airflow Af generated by the airflow generator  13  (fan or blower) passes through the ventilation passage  5 . One or more ventilation holes  7  may be provided in a downstream section of the ventilation passage  5  in the direction of the airflow Af. Although the airflow generator  13  basically supplies air to the ventilation passage  5 , the airflow generator  13  may also serve to discharge air from the ventilation passage  5 . 
     A representative example of the powder processing apparatus according to the exemplary embodiment will now be described. 
     The ventilation passage  5  may pass by the collecting openings  3  of the collecting container  2 . In this example, the heat-melting powder that has been transported to the collecting openings  3  is cooled, so that clogging of the powder, which easily melts, is suppressed. When plural collecting openings  3  are provided, the ventilation passage  5  may pass by all of the collecting openings  3 . However, the ventilation passage  5  may instead pass by at least one of the collecting openings  3 . 
     The ventilation holes  7  may open toward a space around the powder processing units  12  in the housing  11 . In this example, the airflow Af flows toward the space around the powder processing units  12  from the ventilation holes  7 , so that contamination of the environment around the powder processing units  12  is suppressed. 
     A member that defines the ventilation passage  5  may be removably attachable to the collecting container  2 . In this example, since the member that defines the ventilation passage  5  is removably attached to the collecting container  2 , the collecting container  2  additionally provides a ventilation function as necessary. 
     The member that defines the ventilation passage  5  may be attached to the exterior wall of the collecting container  2 . In this case, the member that defines the ventilation passage  5  may be attached to the exterior wall of the collecting container  2  at any location without taking, for example, the layout of components disposed in the collecting container  2  into consideration. 
     The ventilation passage  5  may be disposed above the collecting openings  3  in the collecting container  2 . In this example, since the ventilation passage  5  is disposed above the collecting openings  3  in the collecting container  2 , the region around the collecting openings  3  disposed below the ventilation passage  5  is cooled by the airflow Af that flows through the ventilation passage  5 . 
     A representative example of the collecting container  2  contains a transporting member  4  that is disposed below the collecting openings  3  and that transports the collected powder. The collecting container  2  has a discharge opening (not shown) at the bottom of a downstream section of the collecting container  2  in a direction in which the transporting member  4  transports the powder. The powder is discharged through the discharge opening and stored in a disposal container  17 . In this example, the powder collected from the powder processing units  12  is transported to the disposal container  17 . The collecting container  2  provided with the ventilation passage  5  is used not for disposal but to transport the collected powder. 
     A representative example of the processing apparatus  10  includes a first airflow generator (which corresponds to the airflow generator  13 ) and a second airflow generator  14 . The first airflow generator is disposed at one front corner of the housing  11  and generates the airflow Af toward the inlet  6  of the ventilation passage  5 . The second airflow generator  14  is disposed at a corner of a rear section of the housing  11 , the rear corner being diagonally opposite the location of the first airflow generator  13 . The second airflow generator  14  generates airflow in such a direction that the airflow Af that has flowed into the space in the housing  11  from the ventilation holes  7  in the ventilation passage  5  flows out of the housing  11 . In this example, the first airflow generator  13  and the second airflow generator  14  are disposed in the housing  11 , and the airflow Af introduced through the ventilation passage  5  of the powder collecting device  1  is guided into the space in the housing  11  and toward the powder processing units  12 . Since the first airflow generator  13  and the second airflow generator  14  are diagonally opposite each other, the airflow Af flows over the entire region of the space in the housing  11 . 
     As illustrated in  FIG. 1C , the processing apparatus  10  may include the airflow generator  13  that is disposed at one front corner of the housing  11  and that generates airflow; an upper branch pipe (not shown) through which a portion of the airflow Af generated by the airflow generator  13  branches off upward and is guided to the inlet  6  of the ventilation passage  5 ; a lower branch pipe (not shown) through which a portion of the airflow Af generated by the airflow generator  13  branches off downward; and a lower ventilation passage  18  that is disposed below the powder processing units  12  in the housing  11  and that is partitioned from a space in the housing  11 . The lower ventilation passage  18  has an inlet  18   a  connected to the lower branch pipe, and a ventilation hole  18   b  that opens toward a space below the powder processing units  12 . In this example, the airflow Af generated by the airflow generator  13  is divided into upward and downward airflows. The upward airflow is guided into the space in the housing  11  through the ventilation passage  5  of the powder collecting device  1  as upper airflow. The downward airflow is guided into the space in the housing  11  through the lower ventilation passage  18  as lower airflow. 
     When the present invention is applied to an image forming apparatus that is the processing apparatus  10  that uses developer as the powder, each powder processing unit  12  may include an image carrier  15  capable of carrying an electrostatic latent image; a developing device (not shown) that develops the electrostatic latent image on the image carrier  15  into a visible image by using developer that serves as the powder; a transfer device  16  that transfers the visible image developed by the developing device onto a recording medium; and a cleaning device (not shown) that removes the developer that remains on the image carrier  15 . The powder collecting device  1  collects the developer transported from at least one of the cleaning device, the transfer device  16 , or the developing device. 
     In this example, the developer that has been removed by the cleaning device is collected. When the transfer device  16  is, for example, an intermediate transferring device, the developer removed by a cleaning device for an intermediate transfer body  16   m  is collected. When the transfer device  16  is a direct transferring device, the developer removed by a cleaning device attached to a transfer member is collected. When two-component developer containing toner and carrier, for example, is used in the developing device, the toner is consumed while the carrier is not consumed. Therefore, when the developer becomes old, there is a risk that the charging characteristics will be adversely affected. To avoid this, the old developer is collected. 
     In a representative example of the image forming apparatus that is the processing apparatus  10  that uses the developer as the powder, the powder collecting device  1  collects at least the developer transported from the cleaning device. The ventilation holes  7  in the ventilation passage  5  face a space above or beside the cleaning device of each powder processing unit  12  or a space above the developing device of each powder processing unit  12 . 
     The cleaning device generally includes a transporting member that transports the removed developer toward the powder collecting device  1 . Since the developing devices uses toner as the developer, a toner cloud is easily generated around the developing devices. In this example, the ventilation holes  7  in the ventilation passage  5  face a space above or beside the cleaning device. Therefore, the airflow Af that flows around the cleaning device cools the transporting member that transports the developer toward the powder collecting device  1 , thereby reducing the risk that the developer will adhere to the transporting member. In addition, the ventilation holes  7  in the ventilation passage  5  face the space above the developing devices. Therefore, even when there is a toner cloud that floats around the developing devices, the airflow Af that flows around the developing devices blows the toner cloud away, and the toner may be collected by a filter or the like (not shown). 
     In another representative example of this type of image forming apparatus, the transfer device  16  includes the intermediate transfer body  16   m  onto which the visual images formed on the image carriers  15  by using the developer are transferred before being transferred onto the recording medium S. The intermediate transfer body  16   m  is disposed above the image carriers  15 . The ventilation holes  7  in the ventilation passage  5  face a space below the intermediate transfer body  16   m . In this example, when the intermediate transfer body  16   m  is disposed above the image carriers  15  in an intermediate-transfer image forming apparatus, the ventilation holes  7  in the ventilation passage  5  of the powder collecting device  1  face the space below the intermediate transfer body  16   m . Even when there is a toner cloud that floats around the developing devices, the toner cloud does not adhere to the intermediate transfer body  16   m , and is blown away by the airflow Af discharged from the ventilation passage  5  through the ventilation holes  7 . 
     The present invention will be described in more detail based on an exemplary embodiment illustrated in the attached drawings. 
     Exemplary Embodiment 1 
       FIG. 2  is a perspective view illustrating the overall structure of an image forming apparatus  20 , which serves as a powder processing apparatus according to Exemplary Embodiment 1. 
     Referring to  FIG. 2 , the image forming apparatus  20  includes a housing  21  that houses image forming elements. The image forming elements includes an imaging element that forms an image on a recording medium and an image reading element (not shown) that reads a document image to be formed on the recording medium (not shown). 
     In the present exemplary embodiment, the imaging element includes image forming units  30  (more specifically, image forming units  30   a  to  30   d ) that electrophotographically form plural color images; an intermediate transfer body  40  that is, for example, belt-shaped and onto which the images formed by the image forming units  30  are temporarily transferred before being transferred onto the recording medium; and a simultaneous transfer device  50  that transfer the color images that have been transferred to the intermediate transfer body  40  onto the recording medium. The recording medium is supplied from a recording-medium supplying device  60 , which is disposed below the image forming units  30 , and is transported by a transport roller  62  disposed on a transport path  61  that extends substantially vertically. The images on the intermediate transfer body  40  are simultaneously transferred onto the recording medium in a transferring section of the simultaneous transfer device  50 . The images are fixed to the recording medium by a fixing device  70  disposed in a downstream section of the transport path  61 . The recording medium is ejected onto a recording-medium receiving unit  24 , which will be described below, by an ejection roller  63  disposed immediately in front of the recording-medium receiving unit  24 . 
     Each of the image forming units  30  ( 30   a  to  30   d ) includes a photoconductor  31  that is, for example, drum-shaped; a charging unit  32  that charges the photoconductor  31 ; an exposure unit  33  that is composed of, for example, a writing head of an LED print head or the like and which optically forms an electrostatic latent image on the charged photoconductor  31 ; a developing unit  34  which develops the electrostatic latent image on the photoconductor  31  with color toner of a predetermined color; a transfer unit  35  that transfers the developed image on the photoconductor  31  onto the intermediate transfer body  40 ; and a cleaning unit  36  that removes residual toner from the photoconductor  31 . 
     Toners of different colors are supplied to the developing units  34  of the image forming units  30  from toner cartridges  38  ( 38   a  to  38   d ). 
     Each developing unit  34  uses a two-component developer that contains toner and carrier. A one-component developer, which does not contain carrier, may of course be used instead. 
     In the present exemplary embodiment, the intermediate transfer body  40  is wrapped around plural stretching rollers  41  to  44 . The stretching roller  41 , for example, serves as a driving roller for rotating the intermediate transfer body  40 . An intermediate-transfer-body cleaning unit  45  is disposed downstream of the simultaneous transfer device  50  in a transporting direction of the intermediate transfer body  40 . The intermediate-transfer-body cleaning unit  45  removes residual toner from the intermediate transfer body  40 . 
     The simultaneous transfer device  50  includes a simultaneous transfer roller  51  that opposes an opposing roller, which is the stretching roller  42  for the intermediate transfer body  40 . The intermediate transfer body  40  is sandwiched between the simultaneous transfer roller  51  and the opposing roller. A transfer voltage is applied across the simultaneous transfer roller  51  and the opposing roller, which is the stretching roller  42 , so that a transfer electric field is generated therebetween. 
     Developer-Collecting System 
     In the present exemplary embodiment, as illustrated in  FIGS. 3 to 5 , a developer-collecting system, which is mounted in the housing  21 , is exposed when a front covering  21   a  is opened. The front covering  21   a  is provided on the user&#39;s side (front) of the housing  21 . The developer-collecting system collects the developer, which serves as powder, used in the image forming units  30  (waster toner and waste developer in this example). The developer-collecting system of this example includes a developer-transporting unit  100  and a developer-collecting box  200 . The developer-transporting unit  100  collects and transports the developer from the image forming units  30  and the intermediate transfer body  40 . The developer-collecting box  200  collects the developer transported by the developer-transporting unit  100  for disposal. 
     Developer-Transporting Unit 
     In the present exemplary embodiment, the developer-transporting unit  100  is removably attachable to the housing  21  by moving the developer-transporting unit  100  in a front-to-back direction along an approximately linear path. The developer-transporting unit  100  is disposed in a front section of the housing  21  at a predetermined set position. In this example, the developer-transporting unit  100  collects the developer discharged through the following three systems: 
     (1) The cleaning units  36  included in the image forming units  30  ( 30   a  to  30   d ) remove the developer (waste toner) that remains on the photoconductors  31 . Each cleaning unit  36  includes a transporting member that discharges the removed waste toner from one end of a waste container. As illustrated in  FIGS. 5 to 7 , the discharged waste toner is collected by the developer-transporting unit  100  through waste-toner discharging units  90  (more specifically, waste-toner discharging units  90   a  to  90   d ). 
     (2) The intermediate-transfer-body cleaning unit  45  removes the developer (waste toner) that remains on the intermediate transfer body  40 . The intermediate-transfer-body cleaning unit  45  includes a transporting member that discharges the removed waste toner from one end of a waste container. As illustrated in  FIGS. 5 to 7 , the discharged waste toner is collected by the developer-transporting unit  100  through a waste-toner discharging unit  91 . 
     (3) The developing units  34  included in the image forming units  30  ( 30   a  to  30   d ) each include a developing roller and plural stirring-transporting members disposed in a developing container. The stirring-transporting members charge the developer while stirring the developer. The carrier contained in the developer is not consumed and remains in the developing container. Therefore, when the carrier contained in the developer becomes old, there is a risk that the charging characteristics of the developer will be adversely affected. To avoid this, in this example, old developer (waste developer) is periodically discharged from the developing container. As illustrated in  FIGS. 5 to 7 , the discharged waste developer is collected by the developer-transporting unit  100  through waste-developer discharging units  92  (more specifically, waste-developer discharging units  92   a  to  92   d ). 
     Structure of Developer-Transporting Unit 
     As illustrated in  FIGS. 3 to 8 , in the present exemplary embodiment, the developer-transporting unit  100  includes a collecting container  110  having a substantially hollow rectangular parallelepiped shape. A transport duct  120 , through which the collected developer is transported, is disposed in the collecting container  110 . A transporting member  130  including, for example, a rotating shaft  131  and a helical blade  132  integrated with the rotating shaft  131  at the periphery thereof is disposed in the transport duct  120 . The collected developer is transported to the developer-collecting box  200 . 
     Collecting Opening and Discharge Opening 
     In this example, as illustrated in  FIGS. 6 and 7 , collecting openings  111  are formed in the collecting container  110 . The collecting openings  111  are connectable to the waste-toner discharging units  90  for the cleaning units  36  of the image forming units  30 . A connection duct  112  is disposed between each collecting opening  111  and the transport duct  120 . A collecting opening  114  is also formed in the collecting container  110 . The collecting opening  114  is connectable to the waste-toner discharging unit  91  for the intermediate-transfer-body cleaning unit  45 . A connection duct  115  is disposed between the collecting opening  114  and the transport duct  120 . Furthermore, collecting openings  117  are also formed in the collecting container  110 . The collecting openings  117  are connectable to the waste-developer discharging units  92  for the developing units  34  of the image forming units  30 . Connection openings  118  that are connectable to discharge openings of the waste-developer discharging units  92  are formed in the transport duct  120  at locations corresponding to the collecting openings  117 . 
     In the present exemplary embodiment, the transport duct  120  has a discharge opening  121 , which faces downward, in a downstream section thereof in the transporting direction of the developer. The discharge opening  121  is opened or closed by a shutter mechanism (not shown). 
     Thus, in this example, the developer-transporting unit  100  is configured so that the used developer from the image forming units  30  and the intermediate transfer body  40  is collected into the collecting container  110 , dropped into the transport duct  120 , transported by the transporting member  130  in the transport duct  120 , and then collected into the developer-collecting box  200  through the discharge opening  121 . 
     Developer-Collecting Box 
     In the present exemplary embodiment, as illustrated in  FIGS. 3 to 6 , the developer-collecting box  200  is disposed below the discharge opening  121  in the collecting container  110  of the developer-transporting unit  100 . The developer-collecting box  200  includes a collecting container  210  having a substantially hollow rectangular parallelepiped shape that extends in a direction substantially perpendicular to the direction in which the collecting container  110  extends. The collecting container  210  includes a connection duct  211  that is connectable to the discharge opening  121  in the developer-transporting unit  100  when the developer-transporting unit  100  is at the predetermined set position. The collecting container  210  is disposed so that a connection opening  212  formed in the connection duct  211  is connected to the discharge opening  121 . Furthermore, in this example, a transporting member  220  is disposed in the collecting container  210 . The transporting member  220  transports the developer in the longitudinal direction of the collecting container  210  while stirring the developer. The transporting member  220  of this example includes, for example, a rotating shaft and a helical blade integrated with the rotating shaft at the periphery thereof. However, any type of transporting member may be used as long as the member has a function of transporting and stirring the developer. 
     Ventilation Structure for Developer-Transporting Unit 
     In the present exemplary embodiment, a first fan  141  (see  FIG. 15 ) that generates airflow is disposed at one front corner of the housing  21 , and a second fan (not shown) is disposed at one rear corner of the housing  21 . In this example, the rear corner is diagonally opposite the location of the first fan  141 . The first fan  141  generates airflow in such a direction that air is supplied to the space in the housing  21 . The second fan generates airflow in such a direction that air is discharged from the housing  21 . In this example, a filter (not shown) for removing powder, such as toner, is disposed in a portion of the region in which airflow is generated by the second fan. 
     In the present exemplary embodiment, as illustrated in  FIGS. 8 to 10 , the developer-transporting unit  100  includes a ventilation duct  150  that is removably attached to an exterior wall (inner exterior wall) of the collecting container  110  that faces the space in the housing  21 . 
     Structure of Ventilation Duct 
     In the present exemplary embodiment, the ventilation duct  150  is a long member that extends in a longitudinal direction of the collecting container  110  (axial direction of the transporting member  130 ) along an upper section of the inner exterior wall of the collecting container  110 . An end portion of the ventilation duct  150  near the first fan  141  has an inlet  151  through which the airflow from the first fan  141  is introduced. The ventilation duct  150  includes a tubular portion  152 , which has a substantially rectangular cross section, in a region near the inlet  151 , and a channel portion  153 , which has a substantially U-shaped cross section, in a region other than the region of the tubular portion  152 . In this example, the ventilation duct  150  includes a ventilation passage  154  that is connected to the inlet  151  in the tubular portion  152  and that is defined between the channel portion  153  and the inner exterior wall of the collecting container  110  in the region other than the region of the tubular portion  152 . 
     The channel portion  153  of the ventilation duct  150  includes a pair of arms, and plural protruding portions  155  that protrude downward are formed on the lower one of the pair of arms. Each protruding portion  155  has a recessed groove  156  that extends over the entire length of the protruding portion  155  in the direction in which the arms of the channel portion  153  project. Each recessed groove  156  has an opening that functions as a ventilation hole  157  at the end thereof near the connecting portion between the arms of the channel portion  153 . 
     In the present exemplary embodiment, as illustrated in  FIG. 15 , an upper branch pipe  142  that extends upward is disposed near the first fan  141 . The upper branch pipe  142  is connected to the inlet  151  of the ventilation duct  150 . Referring to  FIGS. 8 and 9 , a grip portion  135  is held by a user when the developer-transporting unit  100  is attached or removed. The developer-transporting unit  100  is retained in the housing  21  by a hook  136 . 
     Ventilation Duct Attachment Structure 
     The ventilation duct  150  includes plural substantially L-shaped attachment portions  161  on the top and bottom longitudinal edges thereof. In this example, four attachment portions are provided at the bottom, and three attachment portions are provided at the top. Each attachment portion  161  is formed of an elastically deformable plate, and has an engagement hole  162 . 
     Attachment holes  163  that correspond to the attachment portions  161  of the ventilation duct  150  are formed in the exterior wall of the collecting container  110  to which the ventilation duct  150  is attached. Each attachment hole  163  has an engagement step portion (not shown) that is engageable with the engagement hole  162  in the corresponding attachment portion  161 . Positioning portions  165  are provided near both ends of the ventilation duct  150  in the longitudinal direction. The positioning portions  165  have positioning holes  166  formed therein. Positioning pins  167  that correspond to the positioning holes  166  in the ventilation duct  150  are formed on the exterior wall of the collecting container  110 . 
     Referring to  FIG. 9 , when the ventilation duct  150  is attached to the collecting container  110 , the ventilation duct  150  is positioned so that the two positioning pins  167  on the collecting container  110  extend through the respective positioning holes  166  in the ventilation duct  150 . After that, the ventilation duct  150  is pushed against the collecting container  110 . In this state, the attachment portions  161  of the ventilation duct  150  are inserted into the respective attachment holes  163  in the collecting container  110 , and the engagement step portions (not shown) are snap-fitted into the engagement holes  162  in the respective attachment portions  161 , so that the attachment portions  161  are attached to the attachment holes  163 . 
     When the ventilation duct  150  is removed from the collecting container  110 , the user may hold portions of the ventilation duct  150  near both ends thereof in the longitudinal direction, and pull the ventilation duct  150  away from the collecting container  110 . Accordingly, the attachment portions  161  snap out of the attachment holes  163 , and the ventilation duct  150  is removed from the collecting container  110 . 
     Example of Arrangement of Ventilation Duct and Ventilation Hole 
     In the present exemplary embodiment, the collecting container  110  of the developer-transporting unit  100  has the collecting openings  111  connectable to the waste-toner discharging units  90  for the cleaning units  36 ; the collecting opening  114  connectable to the waste-toner discharging unit  91  for the intermediate-transfer-body cleaning unit  45 ; and the collecting openings  117  connectable to the waste-developer discharging units  92  for the developing units  34 . In this example, the waste toner discharged from the cleaning units  36  has a higher toner density, and therefore melts more easily, than the waste toner discharged from the intermediate-transfer-body cleaning unit  45  and the waste toner contained in the waste developer discharged from the developing unit  34 . 
     Accordingly, in the present exemplary embodiment, as illustrated in  FIG. 8 , the ventilation duct  150  is disposed so as to pass by the collecting openings  111  (four collecting openings  111  in this example) connectable to the waste-toner discharging units  90  of the cleaning units  36 . Thus, the airflow Af that flows through the ventilation duct  150  cools the regions around the collecting openings  111 . 
     In addition, in the present exemplary embodiment, the ventilation passage  154  of the ventilation duct  150  is partitioned from the space in the collecting container  110 . Therefore, the airflow Af in the ventilation passage  154  does not flow into the space in the collecting container  110 , and the waste toner and waste developer collected into the collecting container  110  are not blown away by the airflow Af. 
     In the present exemplary embodiment, the ventilation duct  150  has five ventilation holes  157 . As illustrated in  FIGS. 9 to 14 , the ventilation holes  157  are arranged so as to face the image forming units  30  ( 30   a  to  30   d ) in the housing  21 . 
     More specifically, as illustrated in  FIGS. 11 to 15 , the ventilation holes  157  face the spaces above or beside the cleaning units  36  or the spaces above the developing units  34 . Also, the ventilation holes  157  face the space below the intermediate transfer body  40 . 
     Therefore, in the present exemplary embodiment, as indicated by the arrows in  FIG. 15 , the airflow Af generated by the first fan  141  flows through the upper branch pipe  142 , enters the ventilation passage  154  through the inlet  151  of the ventilation duct  150 , and flows toward the image forming units  30  ( 30   a  to  30   d ) through the ventilation holes  157 . 
     Since the ventilation holes  157  face the spaces above or beside the cleaning units  36 , the airflow Af that flows into the housing  21  from the ventilation holes  157  cools the regions around the transporting members of the waste-toner discharging units  90 . 
     In addition, since the ventilation holes  157  face the spaces above the developing units  34 , even when a toner cloud is generated around the developing units  34 , the airflow Af that flows out of the ventilation holes  157  blows away the toner cloud in a predetermined direction. In addition, in this example, the second fan (not shown) generates airflow in a discharging direction, so that the toner cloud blown away in the predetermined direction is further blown by the airflow Af generated by the second fan. In this state, since a filter is disposed at an intermediate location of the path of the airflow Af, the toner cloud is effectively collected by the filter. 
     In addition, in the present embodiment, the ventilation holes  157  face the space below the intermediate transfer body  40 . Therefore, the airflow Af discharged from the ventilation holes  157  flows along the surface of the intermediate transfer body  40  in the front-to-back direction of the housing  21 , so that the toner cloud and dust do not easily adhere to the surface of the intermediate transfer body  40 . In particular, in the space between two adjacent image forming units  30 , the airflow Af discharged from the corresponding ventilation hole  157  flows in the front-to-back direction of the housing  21  through a passage space surrounded by the intermediate transfer body  40 , the developing unit  34  of one of the two adjacent image forming units  30 , and the cleaning unit  36  of the other of the two adjacent image forming units  30 . 
     Lower Ventilation Structure of Housing 
     In the present exemplary embodiment, a lower ventilation structure that cools the image forming units  30  ( 30   a  to  30   d ) from below is disposed in a lower section of the housing  21 . 
     Referring to  FIG. 15 , this lower ventilation structure includes a lower branch pipe  143  that is disposed near the first fan  141  and extends downward. The lower branch pipe  143  is connected to a lower ventilation duct (not shown) that is separated from the ventilation duct  150  of the developer-transporting unit  100 . The lower ventilation duct has an inlet (not shown) that is connected to the lower branch pipe  143 , and ventilation holes (not shown) that faces the spaces below the image forming units  30 . 
     According to the present exemplary embodiment, the airflow Af from the first fan  141  is guided to the lower ventilation duct (not shown) through the lower branch pipe  143 , and is discharged toward the image forming units  30  ( 30   a  to  30   d ). 
     In this example, the airflow Af from the ventilation holes in the lower ventilation duct (not shown) flows toward the developing units  34 , the cleaning units  36 , and the exposure units  33  of the image forming units  30 , and cools these units. For example, in each developing unit  34 , when a layer-thickness regulating member (not shown) comes into contact with the developing roller, a large amount of heat is generated due to wearing of the layer-thickness regulating member. However, the amount of heat generated due to wearing of the layer-thickness regulating member may be effectively reduced by the airflow Af from the lower ventilation duct. In addition, even when each cleaning unit  36  generates heat due to wearing of the waste-toner transporting member, or when each exposure unit  33  generates heat, the amount of heat generated may be effectively reduced by the airflow Af from below. 
     Maintenance of Image Forming Units and Intermediate Transfer Body 
     When, for example, maintenance is performed on the photoconductors  31  or the developing units  34  of the image forming units  30  ( 30   a  to  30   d ) or on the intermediate transfer body  40 , the image forming units  30  and the intermediate transfer body  40  may be removed toward the front after removing the developer-transporting unit  100  disposed at the front of the housing  21 . Since the ventilation duct  150  is attached to the developer-transporting unit  100 , it is not necessary to remove the ventilation duct  150  when the developer-transporting unit  100  is removed together with the ventilation duct  150 . 
     The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.