Patent Publication Number: US-2023161291-A1

Title: Channel switching device, image forming apparatus, and liquid discharge apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2021-188831, filed on Nov. 19, 2021, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     Embodiments of this disclosure relate to a channel switching device, an image forming apparatus, and a liquid discharge apparatus. 
     Related Art 
     An image forming apparatus collects scattered toner or ozone generated in a development device or a transfer device. The toner or ozone is suctioned, and the suctioned toner or ozone is separated by a collection device. The separated toner or ozone is recovered in a reservoir, and toner or ozone that cannot be separated is collected by a filter. 
     SUMMARY 
     A channel switching device includes: an accommodation portion in which a unit is detachably accommodated; a first channel; a second channel passing through the accommodation portion; and a switch separating the first channel and the second channel, the switch including: a first communication portion communicating with the first channel and the second channel; and a second communication portion disposed at a different position with the first communication portion, the second communication portion communicating with the first channel and the second channel, and the switch configured to switch to one of the first communication portion or the second communication portion in response to an attachment or detachment of the unit to the accommodation portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein: 
         FIG.  1    is a schematic view illustrating a configuration example of an image forming apparatus according to the present embodiment in a state in which a collection unit is detached; 
         FIG.  2    is a schematic view illustrating a configuration example of the image forming apparatus according to the present embodiment in a state in which the collection unit is attached; 
         FIG.  3    is a diagram illustrating a configuration example of a channel switching device according to the present embodiment; 
         FIG.  4    is a diagram illustrating an example of a state of a switch when the collection unit is attached to the channel switching device illustrated in  FIG.  3   ; 
         FIG.  5    is a sectional view illustrating a connection relation between a slide plate and a flexible shutter; 
         FIGS.  6 A and  6 B  are sectional views respectively illustrating an example of the periphery of a second communication portion in a state in which an auxiliary filter is detached, and an example of the periphery of the second communication portion in a state in which the auxiliary filter is attached; 
         FIG.  7    is a schematic view illustrating a configuration example of the collection unit; 
         FIG.  8    is a sectional view of the channel switching device taken along the line VIII-VIII of  FIG.  3   ; 
         FIG.  9    is a sectional view illustrating an example of a state in which the collection unit is attached to the channel switching device illustrated in  FIG.  8   ; 
         FIG.  10    is a diagram illustrating an example of a state before a cover is attached to the channel switching device illustrated in  FIG.  3   ; 
         FIG.  11    is a diagram illustrating an example of a state after the cover is attached to the channel switching device illustrated in  FIG.  3   ; and 
         FIG.  12    is a diagram illustrating a modification of the slide plate. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. 
     DETAILED DESCRIPTION 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this 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 have a similar function, operate in a similar manner, and achieve a similar result. 
     Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Hereinafter, embodiments are described with respect to the drawings. In the drawings for explaining the following embodiments, the same reference codes are allocated to elements, members, or components having the same function or shape and redundant descriptions thereof are omitted below. 
     Descriptions are hereinafter given of a configuration example of a channel switching device  200  according to the present embodiment and a configuration example of an image forming apparatus  1  in which the channel switching device  200  of the present embodiment is employed. Herein, a case in which a collection unit  100  that collects a predetermined substance such as toner and ozone from the air is used as a unit detachable from the channel switching device  200  is described as one example. The collection unit  100  may also be referred simply as a “unit  100 ”. 
     The configuration example of the image forming apparatus  1  in which the channel switching device  200  of the present embodiment is employed is described with reference to  FIGS.  1  and  2   . 
       FIG.  1    is a schematic view illustrating a configuration example of the image forming apparatus  1  according to the present embodiment in a state in which the collection unit  100  is detached. 
       FIG.  2    is a schematic diagram illustrating a configuration example of the image forming apparatus  1  according to the present embodiment in a state in which the collection unit  100  is attached. 
     The image forming apparatus  1  of the present embodiment forms an image on a sheet by using an electrophotographic method. The image forming apparatus  1  is a tandem color image forming apparatus by which four color toners of yellow (Y), magenta (M), cyan (C), and black (K) are overlapped. Hereinafter, the four color toners are referred to as Y, M, C, and K. 
     As illustrated in  FIGS.  1  and  2   , the image forming apparatus  1 , for example, includes a substantially cuboid apparatus body  1 A that forms an exterior of the image forming apparatus  1 . In the apparatus body  1 A, a sheet storage  10 , an image reader  20 , an image forming device  30 , a fixing device  40 , a controller  50 , and the channel switching device  200  are disposed. 
     The sheet storage  10  is disposed in a lower portion of the image forming apparatus  1 . The sheet storage  10  includes a plurality of trays for different sizes of sheets or different types of sheets. A sheet is fed from a tray and then conveyed to a conveyance unit  12 , so that the sheet is conveyed to the image forming device  30  and the fixing device  40  by the conveyance unit  12 . 
     The image reader  20  reads an image of a document to generate image data. The image reader  20  also performs various processes such as a correction process and a compression process on the image data generated by analog/digital (A/D) conversion, and stores the resultant image data in a storage unit of the controller  50 . The image data is not limited to data to be output from the image reader  20 . The image data may be data that is received from a personal computer connected to the image forming apparatus  1  or an external device such as another image forming apparatus. 
     The image forming device  30  forms an image on a sheet based on an image formation job. The image forming device  30  includes four image forming units  30 Y,  30 M,  30 C, and  30 K for the respective color components of Y, M, C, and K, an intermediate transfer belt  33 , primary transfer units  34 , and a secondary transfer roller  35 . 
     Each of the image forming units  30 Y,  30 M,  30 C, and  30 K includes a photoconductor  31  having a drum shape, a development unit  32 , a charging unit, an exposure unit, and a cleaning unit. The development unit  32 , the charging unit, the exposure unit, and the cleaning unit are disposed around the photoconductor  31 . 
     The charging unit charges a surface of the photoconductor  31 , and the exposure unit emits a laser light to the charged surface of the photoconductor  31 . Such irradiation of the photoconductor  31  with the light forms an electrostatic latent image on the photoconductor  31 . The development unit  32  uses a development roller  32   a  to supply a predetermined color toner (any of Y, M, C, and K) to the photoconductor  31  which has been irradiated with the laser light, thereby developing the electrostatic latent image formed on the photoconductor  31 . 
     The images (single color images) formed with the respective Y, M, C, and K toners on the four photoconductors  31  for Y, M, C, and K are transferred from the photoconductors  31  to the intermediate transfer belt  33 . The intermediate transfer belt  33  is an endless belt looped around a plurality of conveyance rollers. The intermediate transfer belt  33  is rotated with rotation of each of the conveyance rollers. On an inner circumferential side of the intermediate transfer belt  33 , the primary transfer units  34  are disposed in positions opposite the respective photoconductors  31  of the image forming units  30 Y,  30 M,  30 C, and  30 K. The primary transfer unit  34  applies a voltage having a polarity opposite to the toner to the intermediate transfer belt  33 , so that the toner adhering to the photoconductor  31  is transferred to the intermediate transfer belt  33 . 
     With the rotation of the intermediate transfer belt  33 , the toner images formed by the four image forming units  30 Y,  30 M,  30 C, and  30 K are sequentially transferred to a surface of the intermediate transfer belt  33 . That is, the toner images having the respective color components of Y, M, C, and K overlap one another to form a color image on the intermediate transfer belt  33 . 
     On an outer circumferential side of the intermediate transfer belt  33 , the secondary transfer roller  35  is disposed in a position opposite the intermediate transfer belt  33 . A nip portion in which the secondary transfer roller  35  and the intermediate transfer belt  33  contact each other is a transfer position. The secondary transfer roller  35  causes the sheet conveyed by the conveyance unit  12  to contact the intermediate transfer belt  33  to transfer the toner image formed on the outer circumferential surface of the intermediate transfer belt  33  to the sheet. 
     The fixing device  40  is disposed on a sheet ejection side relative to the secondary transfer roller  35 . The fixing device  40  includes a pair of rollers that are a heat roller and a pressure roller. When the sheet passes through a nip portion between the roller pair, heat and pressure are applied to the sheet, so that the toner image transferred to the sheet is fused and fixed. The sheet on which the toner image has been fused and fixed is conveyed to an ejection unit. 
     In addition, suction ducts  36  are disposed above the respective development units  32  of the four image forming units  30 Y,  30 M,  30 C, and  30 K. The suction ducts  36  are ducts through which toner-containing air containing toner scattered in the respective image forming units  30 Y,  30 M,  30 C, and  30 K passes. 
     The air which has passed through the four suction ducts  36  is introduced into the channel switching device  200 . In each of  FIGS.  1  and  2   , a dot-dashed line indicates a flow of the air which passes through the suction duct  36  and is then discharged via the channel switching device  200 . 
     The channel switching device  200  changes a flow of the introduced air depending on whether the collection unit  100  is detached ( FIG.  1   ) or the collection unit  100  is attached ( FIG.  2   ), and discharges the air. The channel switching device  200  includes a switch  300  that includes two communication portions. Assume that a channel through which the introduced air flows to the switch  300  is a first channel, and a channel from the switch  300  to where the air is discharged is a second channel. The switch  300  switches the communication portions to communicate with the first channel and the second channel depending on attachment or detachment of the collection unit  100 , thereby changing a flow of the air. The channel switching device  200  is described in detail below. 
     The controller  50 , for example, includes a central processing unit (CPU) and a storage unit such as a random access memory (RAM) and a read only memory (ROM). The CPU of the controller  50 , for example, reads various programs stored in the ROM, and loads the programs into the RAM to execute various processes such as an image forming process and a toner collection process based on the loaded program. 
     In addition, the image forming apparatus  1  includes a storage and an operation display. The storage includes, for example, a hard disk drive (HDD) and a semiconductor non-volatile memory. In the storage, various programs including a system program and a process program to be executed by the controller  50 , and data used for execution of such programs are stored. The operation display includes a display screen, a display unit for displaying various information on the screen, and an operation unit that is used by a user to input various instructions. 
     Next, a configuration example of the channel switching device  200  according to the present embodiment is described.  FIG.  3    is a diagram illustrating a configuration example of the channel switching device  200  according to the present embodiment.  FIG.  3    illustrates an example of a state in which the collection unit  100  is not attached to the channel switching device  200 .  FIG.  4    is a diagram illustrating an example of a state of the switch  300  when the collection unit is  100  is attached to the channel switching device  200  illustrated in  FIG.  3   . For the sake of convenience in description,  FIG.  4    illustrates an example of a state of the channel switching device  200  excluding the collection unit  100 . 
     The channel switching device  200  includes a case  210  in which an introduction portion  211 , an exit  213 , an accommodation portion  215 , a first duct  231 , and a common duct  233  are arranged. Moreover, the channel switching device  200  includes a fan  250 , an auxiliary filter  270 , a door  291 , and the switch  300 . In the channel switching device  200 , a first channel is a channel that guides the air from the introduction portion  211  to the switch  300 , and a second channel is a channel that guides the air from the switch  300  to the exit  213 . Thus, the second channel is a channel that passes through the accommodation portion  215 . When the collection unit  100  is attached, the second channel is a channel that passes through the accommodation portion  215  via the collection unit  100 . 
     The introduction portion  211  is an opening so that the air is introduced into the apparatus. In  FIG.  4   , four introduction portions  211 Y,  211 M,  211 C, and  211 K are formed for the respective four toners (Y, M, C, and K). Alternatively, the introduction portion  211  may have one opening instead of the four openings. Hereinafter, the four introduction portions  211 Y,  211 M,  211 C, and  211 K are referred to as the introduction portion  211  where distinction is not necessary. 
     The exit  213  is an exit of the air introduced from the introduction portion  211 . The accommodation portion  215  is a space that has an opening and in which the collection unit  100  is detachably accommodated. The collection unit  100  is described below with reference to  FIG.  7   . 
     The first duct  231  is a duct that forms the first channel which guides the air introduced from the introduction portion  211  to the switch  300 . The common duct  233  is a duct that forms a channel (one portion of the second channel) that guides the air which has passed through the accommodation portion  215  to the exit  213  via the fan  250 . The common duct  233  and the accommodation portion  215  form a portion of the second channel. 
     The fan  250  is one example of an air blower that generates a flow of the air from the introduction portion  211  to the exit  213 , and is disposed near the exit  213 . 
     The auxiliary filter  270  is one example of an auxiliary unit that supplements a process that is executed by the collection unit  100 , instead of the collection unit  100 . The auxiliary filter  270  may be configured such that the auxiliary filter  270  can be replaced or cleaned when the channel switching device  200  is cleaned. 
     The door  291  is attached to the case  210  with upper and lower hinges, and is opened or closed depending on attachment or detachment of the collection unit  100 . The door  291  is closed when the collection unit  100  is detached, so that the door  291  serves as an external wall of the channel switching device  200 . On the other hand, when the collection unit  100  is attached, the door  291  is opened with insertion of the collection unit  100  and is sandwiched between the case  210  and the collection unit  100 . The door  29  closes (blocks) the accommodation portion  215  in response to the detachment of the collection unit  100  from the accommodation portion  215 . 
     The switch  300  includes a first communication portion  391  and a second communication portion  393  as two communication portions communicating with the first channel and the second channel. The switch  300  switches the communication portions to communicate with the first channel and the second channel, depending on attachment or detachment of the collection unit  100 . The switch  300  also includes a slide plate  310 , a flexible shutter  330 , an open-close shutter  350 , and a tensile unit  370  that is illustrated in  FIGS.  6 A and  6 B . 
       FIG.  5    is a sectional view illustrating a connection relation between the slide plate  310  and the flexible shutter  330 .  FIGS.  6 A and  6 B  are sectional views of the periphery of the second communication portion  393 .  FIG.  6 A  illustrates an example of a state in which the auxiliary filter  270  is detached, whereas  FIG.  6 B  illustrates an example of a state in which the auxiliary filter  270  is attached. Each of  FIGS.  6 A and  6 B  is a view in which the periphery of the second communication portion  393  illustrated in  FIG.  3    is enlarged. The switch  300  is described in detail with reference to  FIGS.  3  through  6 B . 
     The slide plate  310  is a rectangular plate that slides depending on attachment or detachment of the collection unit  100 . The case  210  has a groove  217 , and the slide plate  310  is fitted into the groove  217 . Thus, the slide plate  310  is slidable along the groove  217 . In addition, the slide plate  310  has a hole  311  through which the air passes. 
     The flexible shutter  330  is a shutter made of a material (e.g., MYLAR®) that not only has flexibility but also is impervious to gas. As illustrated in  FIG.  5   , the flexible shutter  330  is attached so as to be held by a spring clip  331  at an end portion of the slide plate  310 . The case  210  includes a guide wall  395 , and the flexible shutter  330  is attached along the guide wall  395 . 
     The open-close shutter  350  has an opening  351 . The opening  351  communicates with the first communication portion  391  in a case where a channel is switched to the first channel. The open-close shutter  350  has a hole  353  near the flexible shutter  330 . An end portion of the flexible shutter  330  is folded back through the hole  353  of the shutter  350  and attached to a body of the flexible shutter  330  to form a folded-back portion  333 . Thus, the flexible shutter  330  is coupled with the open-close shutter  350 . The case  210  has a groove  219 , and the open-close shutter  350  is fitted into the groove  219 . 
     A lower end portion of the open-close shutter  350  has a hanger  355  that is bent in an L-shape. The tensile unit  370  is an expansion and contraction member formed of an elastic member such as a spring. One end of the tensile unit  370  is hung on the hanger  355 , and the other end of the tensile unit  370  is hung on a support  371  disposed on the case  210 . The hanger  355  is vertically movable in a range of length of a slit hole  397 . 
     The first communication portion  391  is a channel that communicates with the first channel and the second channel in a case where the collection unit  100  is attached. The second communication portion  393  is an opening that communicates with the first channel and the second channel in a case where the collection unit  100  is detached. The second communication portion  393  is formed by the slit hole  397  and an opening  399  such that the air flows. 
     The auxiliary filter  270  is disposed such that not only the air passing through the second communication portion  393  can be processed, but also an area in which the tensile unit  370  expands and contracts can be provided. The auxiliary filter  270  may be disposed to cover the opening  399 . 
     Herein, a description is given of one example of the collection unit  100  detachable from the accommodation portion  215  of the channel switching device  200  according to the present embodiment.  FIG.  7    is a schematic diagram illustrating a configuration example of the collection unit  100 . The collection unit  100 , for example, includes a case  110  formed in a substantially cuboid shape, and the case  110  has an inflow port  111 , an outflow port  113 , and a pressing rib  115 . The collection unit  100  includes a separator  121 , a reservoir  123 , a filter unit  125 , and channels  127  and  129  that are disposed inside the case  110 . 
     The inflow port  111  is an opening into which the air from the first communication portion  391  of the channel switching device  200  flows. The outflow port  113  is an opening from which the air from the collection unit  100  to an auxiliary duct of the channel switching device  200  flows out. 
     The pressing rib  115  contacts the slide plate  310  to cause the slide plate  310  to slide when the collection unit  100  is attached to the channel switching device  200 . The pressing rib  115  includes a fitting portion such as leaf spring such that the fitting portion is fitted into an end portion of the slide plate  310  when the collection unit  100  is attached, and the fitting portion is separated from the slide plate  310  when the collection unit  100  is detached. 
     The separator  121  separates toner from the air which has flowed in from the inflow port  111 . The separator  121 , for example, is formed in a cylindrical shape and disposed such that an axial direction of the separator  121  and a vertical direction match each other. The reservoir  123  stores the toner separated by the separator  121 . The filter unit  125  includes a filter that cleans the air flowing from the separator  121 . The filter unit  125  may include a plurality of types of filters, for example, a toner dustproof filter that filters toner remaining in the air, and an ozone catalyst filter that eliminates ozone. The channel  127  guides the air which has flowed out from the separator  121  to the filter unit  125 , whereas the channel  129  guides the air which has flowed out from the filter unit  125  to the outflow port  113 . The filter unit  125  may also be referred simply as a “filter  125 ”. 
     The separator  121  causes the air introduced inside from a lower portion of the cylindrical shape to swirl to separate toner. The separated toner drops under its own weight and is accumulated in the reservoir  123 . When the collection unit  100  is detached, the accumulated toner is collected. The filter unit  125  cleans the air which has flowed in via the channel  127 , and expels the cleaned air from the outflow port  113  via the channel  129 . A detailed description of the collection unit  100  is omitted herein. The channel switching device  200  according to the present embodiment can employ, for example, a unit that executes a function such as collecting scattered toner or ozone generated in a development device or a transfer device and separating collected toner or ozone by a collection device. The separated toner or ozone is recovered in a reservoir, and toner or ozone that cannot be separated is collected by a filter. 
     Next, an example of an operation performed by the switch  300  when the collection unit  100  is attached to or detached from the accommodation portion  215  of the channel switching device  200  is described with reference to  FIGS.  3 ,  4 ,  8 , and  9   .  FIG.  8    is a sectional view of the channel switching device  200  taken along the line VIII-VIII of  FIG.  3   .  FIG.  9    is a sectional view illustrating an example of a state in which the collection unit  100  is attached to the channel switching device  200  illustrated in  FIG.  8   . In each of  FIGS.  8  and  9   , a dot-dashed line indicates a flow of the air. In  FIG.  9   , each of components inside the case  110  of the collection unit  100  is omitted. 
     When the Collection Unit  100  is Detached 
     When the collection unit  100  is detached from the channel switching device  200 , a state illustrated in  FIG.  4  or  9    shifts to a state illustrated in  FIG.  3  or  8   . Particularly, the slide plate  310  moves in a direction indicated by an arrow A 12  illustrated in  FIG.  8   . Moreover, the flexible shutter  330  and the open-close shutter  350  are pulled and moved in a direction indicated by an arrow A 22  illustrated in  FIG.  8    by the tensile unit  370 . 
     If a state shifts to the state illustrated in  FIG.  3  or  8   , the first communication portion  391  is blocked by the flexible shutter  330  and becomes closed. Meanwhile, the detachment of the collection unit  100  enables the air to pass via the slit hole  397  and the opening  399 , so that the second communication portion  393  communicates with the first channel and the second channel. Moreover, the air passes between the accommodation portion  215  and the common duct  233  by using the hole  311  in the slide plate  310 . Furthermore, the door  291  is closed and becomes an outer wall of the case  210 . 
     Accordingly, in a state in which the collection unit  100  is detached, the air which has introduced from the introduction portion  211  passes through the second communication portion  393  via the auxiliary filter  270  from the first duct  231  and is guided to the accommodation portion  215 . Then, the air passes through the common duct  233  and is discharged to the exit  213 . 
     When the Collection Unit  100  is Attached 
     When the collection unit  100  is attached to the channel switching device  200 , a state illustrated in  FIG.  3  or  8    shifts to the state illustrated in  FIG.  4  or  9   . Particularly, when the collection unit  100  is accommodated in the accommodation portion  215 , the slide plate  310  is pushed and moved in a direction indicated by an arrow A 11  illustrated in  FIG.  9    by the pressing rib  115  disposed to the collection unit  100 . Moreover, with such a slide movement of the slide plate  310 , the flexible shutter  330  and the open-close shutter  350  are pulled and moved in a direction indicated by an arrow A 21  illustrated in  FIG.  9   . 
     If a state shifts to the state illustrated in  FIG.  4  or  9   , the first communication portion  391  is opened by the opening  351  disposed to the open-close shutter  350 , and communicates with the first channel and the second channel. Moreover, a portion between the accommodation portion  215  and the common duct  233  is opened by the movement of the slide plate  310 . On the other hand, in the second communication portion  393 , a flow of the air between the slit hole  397  and the opening  399  is stopped by the attached collection unit  100 . 
     Accordingly, in the state in which the collection unit  100  is attached, the air which has introduced from the introduction portion  211  passes through the first communication portion  391  from the first duct  231 , and is guided to the collection unit  100 . Then, the air passes through the common duct  233  and is discharged to the exit  213 . 
     As described above, the switch  300  is configured such that the flexible shutter  330  moves along the guide wall  395 , and the open-close shutter  350  slides along the groove  219  if the slide plate  310  slides. With the slide movement of the slide plate  310 , the first communication portion  391  is closed and opened by the movement of the open-close shutter  350 . 
     In the channel switching device  200  according to the present embodiment, therefore, any of the first communication portion  391  and the second communication portion  393  communicates with a first channel and a second channel in response to a slide movement of the slide plate  310  in association with attachment or detachment of the collection unit  100 . Thus, the channel switching device  200  disposed in the image forming apparatus  1  as a main apparatus that switches between a channel that passes through the collection unit  100  and a channel that passes through the auxiliary filter  270 . 
     A cover  293  is attached to the channel switching device  200  as illustrated in  FIGS.  10  and  11   , so that the final form of the channel switching device  200  is provided.  FIG.  10    is a diagram illustrating an example of a state before the cover  293  is attached to the channel switching device  200 .  FIG.  11    is a diagram illustrating an example of a state after the cover  293  is attached to the channel switching device  200  illustrated in  FIG.  3   . The cover  293  may be configured to be one portion of an external wall surface of the image forming apparatus  1 . 
     As for the channel switching device  200  as illustrated in  FIGS.  10  and  11   , when the collection unit  100  is detached, the accommodation portion  215  is surrounded by the cover  293  and the door  291 , and a channel from the second communication portion  393  to the hole  311  of the slide plate  310  is formed. The above embodiment has been described using an example in which the slide plate  310  is a rectangular plate on which the hole  311  is formed. However, the slide plate  310  is not limited thereto. The slide plate  310 , for example, may have a shape having a recessed portion (a cut-out) to form a clearance between the slide plate  310  and the cover  293 . Alternatively, the slide plate  310  may be configured such that a clearance can be provided between the slide plate  310  and the case  210  in an area in which the slide plate  310  slides (a movement area in the direction indicated by the arrow A 12  in each of  FIGS.  8  and  9   ). 
     In the above-described embodiment, the channel switching device  200  is preferably configured to be detachable from the image forming apparatus  1 . 
     According to the channel switching device  200  of the present embodiment, in a case where the collection unit  100  is detached from the channel switching device  200  disposed in the image forming apparatus  1 , a communication portion is automatically switched from the first communication portion  391  to the second communication portion  393 , and thus a first channel and a second channel communicate with each other via an auxiliary unit (the auxiliary filter  270 ) that assists a function of the collection unit  100 . Accordingly, the collection unit  100  can be replaced not only without degrading quality of the air to be discharged from the apparatus but also without temporality stopping an operation (without lowering productivity) of the image forming apparatus  1 . 
     For example, an airflow channel toward a first filter and an airflow channel toward a second filter are electrically switched by a switching device to reduce degradation in a cooling effect. In the channel switching device  200  according to the present embodiment, on the other hand, channels can be simply switched by a mechanical operation of detachment and attachment of the collection unit  100  instead of using an electrical component (e.g., a motor, a clutch, a sensor, and a substrate) or control related to switching, so that a malfunction of the electrical component or the control can be prevented. 
     In addition, the use of the channel switching device  200  according to the present embodiment can prevent an increase in costs by arrangement of an electrical switching device (e.g., a motor, a clutch, and a sensor) or can reduce labor or costs for assurance of control reliability with respect to the frequency of channel changes due to filter dirtiness. 
     Moreover, according to the channel switching device  200  of the present embodiment, air-exhaustion-related functions including the collection unit  100  and an airflow switching device are integrated as the channel switching device  200 , and the channel switching device  200  is detachable from the image forming apparatus  1 . Thus, an inside of an air exhaustion unit (a duct) can be readily cleaned (cleanability can be enhanced) without removal of, for example, an exterior of the image forming apparatus  1 . 
     Each of the above embodiments has been described using the collection unit  100  as a unit that is detachably disposed in the channel switching device  200 . However, the unit is not limited thereto. A unit that performs a process for separating or removing an optional substance from the air may be used. In such a case, the process to be performed by the unit can be supplemented by an auxiliary unit instead of the unit. The use of the unit is not limited to the removal of an optional substance from the air. A unit that mixes or adds an optional substance to the air may be employed. 
     The channel switching device  200  has been described using an example of a configuration including the fan  250  as an air blower. However, the channel switching device  200  is not limited thereto. For example, an air blower may be disposed in an apparatus body in which the channel switching device  200  of the present embodiment is disposed. In such a case, a flow of the air may be generated by the channel switching device  200 . 
     The embodiment has been described using a configuration example in which the channel switching device  200  is used in the image forming apparatus  1 . However, the embodiment is not limited thereto. A main apparatus that uses the channel switching device  200  of the present embodiment is not limited to the above-described image forming apparatus  1 . The channel switching device  200  of the present embodiment may be used in a liquid discharge apparatus such as an inkjet apparatus that discharges a liquid. In a case of the inkjet apparatus, since liquid discharged from a recording head floats as mist, a collection unit that collects floating mist can be used as a unit detachable from the channel switching device  200 . Thus, the liquid discharge apparatus such as the inkjet apparatus may be used as an example of the image forming apparatus  1 . 
     In the aforementioned example, a configuration example in which the hole  311  is formed on the slide plate  310  has been described. However, the example is not limited thereto.  FIG.  12    is a diagram illustrating a modification of the slide plate. For example, as illustrated in  FIG.  12   , a channel switching device  200   a  can include a plate (a secured plate)  313  the position of which is secured above a slide plate  310   a  such that a hole  311  is not formed on the slide plate  310   a . In the example illustrated in  FIG.  12   , an opening  312  is formed between a right end of the slide plate  310   a  and a duct auxiliary wall  117 . Unlike the above-described example, a length of the slide plate  310   a  in a lateral width direction is short. In addition, the right end of the slide plate  310   a  is positioned such that the opening  312  is opened when the collection unit  100  is not attached. 
     Aspect 1 
     A channel switching device ( 200 ) includes: an accommodation portion ( 215 ) in which a unit ( 100 ) is detachably accommodated; a first channel ( 231 ); a second channel ( 215 ,  233 ) passing through the accommodation portion ( 215 ); and a switch ( 300 ) separating the first channel ( 231 ) and the second channel ( 215 ,  233 ), the switch ( 300 ) including: a first communication portion ( 391 ) communicating with the first channel ( 231 ) and the second channel ( 215 ,  233 ); and a second communication portion ( 393 ) disposed at a different position with the first communication portion ( 391 ), the second communication portion ( 393 ) communicating with the first channel ( 231 ) and the second channel ( 215 ,  233 ), and the switch ( 300 ) configured to switch to one of the first communication portion ( 391 ) or the second communication portion ( 393 ) in response to an attachment or detachment of the unit ( 100 ) to the accommodation portion ( 215 ). 
     Aspect 2 
     In the channel switching device ( 200 ) according to Aspect 1, the switch ( 300 ) includes a slide plate ( 310 ) configured to slide in response to the attachment and the detachment of the unit ( 100 ) to the accommodation portion ( 215 ). 
     Aspect 3 
     In the channel switching device ( 200 ) according to Aspect 2, the switch ( 300 ) switches to one of opening or closing of the first communication portion ( 391 ) in response to a slide movement of the slide plate ( 310 ). 
     Aspect 4 
     In the channel switching device ( 200 ) according to Aspect 3, the switch ( 300 ) slidably moves the slide plate ( 310 ) to open the first communication portion ( 391 ) and close the second communication portion ( 393 ) in response to the attachment of the unit ( 100 ) to the accommodation portion ( 215 ) to cause the first channel ( 231 ) to communicate with the second channel ( 215 ,  233 ) via the unit( 100 ) in the accommodation portion ( 215 ). 
     Aspect 5 
     In the channel switching device ( 200 ) according to Aspect 3 or 4, the second communication portion ( 393 ) includes an auxiliary filter ( 270 ); and the switch ( 300 ) slidably moves the slide plate ( 310 ) to close the first communication portion ( 391 ) and open the second communication portion ( 393 ) in response to the detachment of the unit ( 100 ) from the accommodation portion ( 215 ) to cause the first channel ( 231 ) to communicate with the second channel ( 215 ,  233 ) via the auxiliary filter ( 270 ). 
     Aspect 6 
     The channel switching device ( 200 ) according to any one of Aspects 1 through 5, further includes a door ( 291 ) configured to be openably closed in response to the attachment or the detachment of the unit ( 100 ) to the accommodation portion ( 215 ), and the door ( 291 ) closes the accommodation portion ( 215 ) in response to the detachment of the unit ( 100 ) from the accommodation portion ( 215 ). 
     Aspect 7 
     In the channel switching device ( 200 ) according to any one of Aspects 1 through 6, the unit ( 100 ) includes a filter ( 125 ) configured to collect a predetermined substance. 
     Aspect 8 
     The channel switching device ( 200 ) according to any one of Aspects 1 through 7, further includes an air blower ( 250 ) configured to generate airflow from the first channel ( 231 ) to the second channel ( 215 ,  233 ). 
     Aspect 9 
     An image forming apparatus ( 1 ) includes the channel switching device ( 200 ) according to any one of Aspects 1 through 8. 
     Aspect 10 
     A liquid discharge apparatus ( 1 ) includes the channel switching device ( 200 ) according to any one of Aspects 1 through 8. 
     The present embodiment has been described above with reference to specific embodiment but is not limited thereto. It is apparent to one skilled in the art that various modifications and enhancements are possible without departing from scope of the disclosure. 
     The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention. Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above. 
     The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, application specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable gate arrays (FPGAs), conventional circuitry and/or combinations thereof which are configured or programmed to perform the disclosed functionality. Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality. The hardware may be any hardware disclosed herein or otherwise known which is programmed or configured to carry out the recited functionality. When the hardware is a processor which may be considered a type of circuitry, the circuitry, means, or units are a combination of hardware and software, the software being used to configure the hardware and/or processor.