IMAGE FORMING APPARATUS HAVING SWIVEL HOUSING BACKGROUND [0001] An image forming apparatus includes a transfer device which conveys a toner image and transfers the toner image to a print medium. The transfer device includes an intermediate transfer belt, a tension roller which extends the intermediate transfer belt, a drive roller which rotationally drives the intermediate transfer belt, a primary transfer roller which primarily transfers the toner image to the intermediate transfer belt, and a secondary transfer roller which secondarily transfers the toner image carried on the intermediate transfer belt to the print medium. Residual toner particles remaining on the intermediate transfer belt without having been transferred from the intermediate transfer belt to the print medium are recovered by a toner recovery device. BRIEF DESCRIPTION OF DRAWINGS [0002] FIG.1 is a schematic view of an example image forming apparatus. FIG. 2 is a partial perspective view of an example toner recovery device, illustrated adjacent an intermediate transfer belt. FIG.3 is a side view of the example toner recovery device. FIG.4 is a cross-sectional partial perspective view of the example toner recovery device. FIG.5 is a side view of the example toner recovery device, illustrated in a folded state. FIG.6 is a cross-sectional partial perspective view of the example toner recovery device, illustrated in the folded state. FIG.7A is a schematic diagram illustrating the example toner recovery device as part of an example transfer device inside an image forming apparatus, in which the transfer device is illustrated in a first position of a removal operation of the transfer device from the image forming apparatus. FIG. 7B is a schematic diagram illustrating a second position of the transfer device in the removal operation. FIG. 7C is a schematic diagram illustrating a third position of the transfer device in the removal operation. FIG. 8A is a schematic diagram illustrating a first position of the example transfer device of an insertion operation of the transfer device into the image forming apparatus. FIG. 8B is a schematic diagram illustrating a second position of the example transfer device in the insertion operation. FIG.9A is a schematic diagram illustrating a latch of the toner recovery device, showing a state in which the latch is disengaged by a disengagement portion of the image forming apparatus. FIG. 9B is a schematic diagram illustrating a second position of the latch relative to the disengagement portion. FIG. 10 is a side view illustrating another example toner recovery device adjacent an intermediate transfer belt. FIG. 11 is another side view of the example toner recovery device of FIG.10, illustrated in another position. FIG.12 is a side view illustrating another example of the image forming apparatus. DETAILED DESCRIPTION [0003] In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. [0004] According to the present disclosure, an example image forming apparatus or device such as a printer, for example, may include a cleaning device which recovers toner from an intermediate transfer belt and a housing which accommodates toner particles recovered from the intermediate transfer belt. The housing may include a swivel portion which rotates around a rotation axis extending in parallel to a longitudinal direction of a tension roller. [0005] An example image forming apparatus (or image forming device) 1 will be described with reference to FIG.1. The example image forming apparatus 1 may form a color image by using colors of cyan, magenta, yellow, and black. The image forming apparatus 1 includes a conveying device 10 which conveys a sheet 5 as a print medium, a plurality of developing devices 20C, 20M, 20Y, and 20K (of which a single one may be referred to herein as a "developing device 20") which develop an electrostatic latent image into respective toner images of the four colors, a plurality of photoconductors 40C, 40M, 40Y, and 40K (oy which a single one may be referred to herein as a "photoconductor 40") having respective surfaces to form the electrostatic latent images, a transfer device 30 on which the toner images of the four colors are layered into a single toner image and which transfers the layered toner image onto the sheet 5, a fixing device 50 which fixes the layered toner image to the sheet 5, and a discharging device 60 which discharges the sheet 5 from the image forming apparatus 1. Additionally, the example image forming apparatus 1 includes a toner recovery device 70 which recovers non-transferred toner particles (or residual toner particles). The conveying device 10, the developing device 20, the transfer device 30, the photoconductor 40, the fixing device 50, the discharging device 60, and the toner recovery device 70 are accommodated inside a casing 15 of the image forming apparatus 1. [0006] The conveying device 10 conveys the sheet 5 corresponding to a print medium (e.g., a paper sheet) onto which an image is to be formed, along a conveying path 12. The sheet 5 is initially accommodated in a cassette 7 in a stacked state and is picked up and conveyed by a feeding roller 11 of the conveying device 10. The conveying device 10 conveys the sheet 5 to reach a transfer region 13 at a timing at which the toner image reaches the transfer region 13 such that the toner image can be transferred onto the sheet 5 at the transfer region 13. [0007] The developing devices 20C, 20M, 20Y, and 20K are provided for respective colors of cyan toner, magenta toner, yellow toner and black toner. Each one of the developing devices 20C, 20M, 20Y, and 20K includes a developing roller 110 which carries toner on the adjacent one of the photoconductors 40C, 40M, 40Y, and 40K. In the developing device 20, a two-component developing agent containing toner and a carrier is used as the developing agent. Namely, in the developing device 20, the toner and the carrier are adjusted to a targeted mixing ratio and are further mixed and stirred to disperse the toner and impart an targeted charge amount. This developing agent is carried on the developing roller 110. The developing agent is conveyed to a developing region facing the photoconductor 40 with a rotation of the developing roller 110. At the developing region, the toner contained in the developing agent carried on the developing roller 110 is transferred to the electrostatic latent image formed on the peripheral surface of the photoconductor 40 so that the electrostatic latent image is developed. [0008] The transfer device 30 conveys the toner images formed by the respective developing devices 20C, 20M, 20Y, and 20K to the transfer region 13 to be transferred to the sheet 5. The transfer device 30 includes an intermediate transfer belt 31 (e.g., an endless belt) onto which the toner images of the respective colors are primarily transferred from the respective photoconductors 40C, 40M, 40Y, and 40K, in a layered manner, so as to form the layered toner image (or composite toner image). The transfer belt 31 conveys the composite toner image to the transfer region 13 to be secondarily transferred onto the sheet 5. The transfer device 30 additionally includes a tension roller 34 which tensions the intermediate transfer belt 31, idler rollers 35 and 36, a drive roller 37 which drives the intermediate transfer belt 31, primary transfer rollers 32C, 32M, 32Y, and 32K which are positioned to interpose the intermediate transfer belt 31 between the primary transfer rollers 32C, 32M, 32Y, and 32K and the respective photoconductors 40C, 40M, 40Y, and 40K, and a secondary transfer roller 33 which is positioned to interpose the intermediate transfer belt 31 between the secondary transfer roller 33 and the drive roller 37. [0009] The photoconductors 40C, 40M, 40Y, and 40K may also be referred to as electrostatic latent image carriers, photoconductor drums, or the like. The four photoconductors 40C, 40M, 40Y, and 40K are provided for respective four colors, and are arranged along the moving direction of the intermediate transfer belt 31. The developing device 20, a charging device 41, an exposure unit 42, and a cleaning device 43 are provided adjacent the photoconductor 40. [0010] The charging device 41 is, for example, a charging roller which contacts the photoconductor 40 to charge the surface of the photoconductor 40 to a predetermined potential. The exposure unit 42 exposes the surface of the photoconductor 40 having been charged by the charging device 41, to a light in accordance with an image to be formed on the sheet 5. Accordingly, a portion of the surface having been exposed to the light of the exposure unit 42 changes in potential so that an electrostatic latent image is formed. The developing devices 20C, 20M, 20Y, and 20K generate respective toner images by developing the electrostatic latent images formed on the respective photoconductors 40C, 40M, 40Y, and 40K, with toner supplied from respective toner tanks 18C, 18M, 18Y, and 18K positioned adjacent the respective developing devices 20C, 20M, 20Y, and 20K. The toner tanks 18C, 18M, 18Y, and 18K are respectively filled with cyan, magenta, yellow, and black toners. The cleaning device 43 recovers the toner remaining on the photoconductor 40 after the toner image formed on the photoconductor 40 is primarily transferred to the intermediate transfer belt 31. [0011] After the toner image has been secondarily transferred onto the sheet 5, fixing device 50 conveys the sheet 5 through a fixing nip region where the sheet is heated and pressed, to adhesively fix the toner image to the sheet 5. The fixing device 50 includes a heating roller 52 which heats the sheet 5 and a pressing roller 54 which is rotationally driven while being pressed against the heating roller 52. The heating roller 52 and the pressing roller 54 are each formed in a cylindrical shape and the heating roller 52 includes a heat source therein, such as a halogen lamp. A contact region between the heating roller 52 and the pressing roller 54 forms a fixing nip region. The toner image is melted and fixed to the sheet 5 when the sheet 5 passes through the fixing nip region. [0012] The discharging device 60 includes discharging rollers 62 and 64 which discharge the sheet 5 with the fixed toner image to the outside of the image forming apparatus 1. [0013] The image forming apparatus 1 further includes a control unit (or controller) 80. The control unit 80 may be a computer including a processor, a storage unit (or storage device), an input device, a display device, and the like to control the operation of the image forming apparatus 1. The storage unit of the control unit 80 stores a control program for controlling various processes performed by the image forming apparatus 1 using the processor. [0014] Hereinafter, the example toner recovery device 70 will be described. The toner recovery device 70 is provided adjacent to the intermediate transfer belt 31 and recovers residual toner particles that remain on the intermediate transfer belt 31 without having been transferred to the sheet 5, after the toner image has been transferred onto the sheet 5 at the transfer region 13. [0015] With reference to FIGS. 2 to 4, the example toner recovery device 70 includes a cleaning roller 71, a blade 72, a conveyor device 73, and a housing 74. [0016] The cleaning roller 71 is disposed between the tension roller 34 and the idler roller 35 and recovers toner particles from the intermediate transfer belt 31. The cleaning roller 71 is a substantially cylindrical roller made of a rigid body such as metal, and extends parallel to the longitudinal direction of the tension roller 34. [0017] The outer peripheral surface of the cleaning roller 71 is in contact with the surface of the intermediate transfer belt 31. The cleaning roller 71 is driven to rotate around the rotation axis AX by an electric motor while being in contact with the surface of the intermediate transfer belt 31. The cleaning roller 71 may rotate in the same direction as the rotation direction of the intermediate transfer belt 31 or in the opposite direction thereto. [0018] The cleaning roller 71 is charged with an electrical bias by receiving a bias power supply during an image formation operation to collect the residual toner particles remaining on the intermediate transfer belt 31. Namely, the toner particles are drawn (or attracted) onto the outer peripheral surface of the cleaning roller 71 with an electrostatic force of the electrical bias. [0019] The two end portions of the cleaning roller 71 are rotatably supported by a support body that also support the two end portions of the tension roller 34. Thus, the toner recovery device 70 is connected to the transfer device 30 via the support body of the cleaning roller 71. [0020] The blade 72 is a scraper made of an elastic or flexible material such as metal or resin, and separates toner particles from the cleaning roller 71. In some examples, the blade 72 is a thin plate or sheet made of stainless steel and extending in the width direction of the intermediate transfer belt 31 (a direction orthogonal to the rotation direction of the intermediate transfer belt 31) and contacts the outer peripheral surface of the cleaning roller 71 to scrape off toner particles adhering to the cleaning roller 71. The cleaning roller 71 and the blade 72 constitute a cleaning device 75 which recovers toner from the intermediate transfer belt 31. [0021] The blade 72 has a substantially rectangular planar shape and includes a contact edge portion 72a and a rear-end edge portion 72b. The contact edge portion 72a extends in a direction parallel to the longitudinal direction of the cleaning roller 71. The contact edge portion 72a comes into contact with the outer peripheral surface of the cleaning roller 71 to scrape off toner particles adhering to the outer peripheral surface of the rotating cleaning roller 71. The rear-end edge portion 72b is disposed on a side opposite to the contact edge portion 72a. The toner particles separated from the cleaning roller 71 by the blade 72 are transferred onto the blade 72 from the contact edge portion 72a toward the rear-end edge portion 72b and are directed to a recovery chamber 74s inside the housing 74. [0022] The blade 72 is interposed between a pair of plate members (or sheet members) 77 and 78 arranged in the thickness direction of the blade 72. The pair of plate members (sheet members) 77 and 78 are fastened to each other, for example, by a fastening member such as a screw. The plate member (sheet member) 78 is attached to a second swivel portion 83 of the housing 74 using a fastening member such as a screw. [0023] The conveyor device 73, for example, a screw conveyor, is provided inside the housing 74, and conveys the residual toner particles accommodated in the recovery chamber 74s, to a toner cartridge as waste toner or recycled toner, as will be described further below. [0024] The housing 74 is connected to the cleaning roller 71 and defines the recovery chamber 74s (cf. FIG. 4). The recovery chamber 74s is a space which stores or accommodates toner particles recovered from the intermediate transfer belt 31. The blade 72 and the conveyor device 73 are arranged inside the recovery chamber 74s. The housing 74 is operable between an unfolded state, for example in a state in which the second swivel portion 83 is disposed at an operational position P1 in FIG. 3, and a folded state, for example a state in which the second swivel portion 83 is disposed at a retraction position P2 illustrated in FIG.5, in such a manner that at least a part of the housing 74 is rotatable around a rotation axis AX. [0025] With reference to FIGS. 2 and 3, the housing 74 includes a fixed portion 81, a first swivel portion 82, and a second swivel portion 83. The fixed portion 81 is an upper portion of the housing 74 that sets a fixed position with respect to the cleaning roller 71. Namely, the fixed portion 81 is rotationally fixed relative to the transfer device 30 and relative to the above-described support body that couples the toner recovery device 70 with the transfer device 30. The fixed portion 81 includes a pair of side walls 81a, an upper wall 81b, and a peripheral wall 81c. The pair of side walls 81a are arranged to face each other, with the recovery chamber 74s formed therebetween in the axial direction of the cleaning roller 71. Each of the pair of side walls 81a is connected to the cleaning roller 71 and has a fan shape that increases in width in a substantially outwardly radial direction with respect to the cleaning roller 71. The upper portion of the side wall 81a of the fixed portion 81 is provided with a concave portion 81e which engages with a convex portion 87a of a latch 85 that will be described further below. [0026] The upper wall 81b is connected to the upper edges of the pair of side walls 81a to cover the recovery chamber 74s from above. The peripheral wall 81c forms a circumferential surface that extends substantially along an arc centered around the center axis (or rotation axis AX) of the cleaning roller 71 and is connected to the pair of side walls 81a and the upper wall 81b. As shown in FIG. 4, the lower end of the peripheral wall 81c is provided with a protrusion wall 81d which protrudes toward the cleaning roller 71. [0027] The first swivel portion 82 is a portion that constitutes an intermediate portion of the housing 74 and is rotatable relative to the fixed portion 81 around the rotation axis AX that is aligned with the center axis of the cleaning roller 71. The first swivel portion 82 includes a pair of side walls 82a and a peripheral wall 82c. The pair of side walls 82a are arranged to face each other, with the recovery chamber 74s formed therebetween in the axial direction of the cleaning roller 71. Each of the pair of side walls 82a is rotatably connected to the cleaning roller 71 and has a fan shape that increases in width in a substantially outwardly radial direction with respect to the cleaning roller 71. [0028] The peripheral wall 82c forms a circumferential surface that extends substantially along an arc centered around the center axis (or rotation axis AX) of the cleaning roller 71 and is connected to the pair of side walls 82a. As shown in FIG. 4, the upper end of the peripheral wall 82c is provided with a protrusion wall 82d which protrudes in a direction pointed away from the cleaning roller 71 and the lower end of the peripheral wall 82c is provided with a protrusion wall 82e which protrudes toward the cleaning roller 71. As shown in FIG. 4, when the first swivel portion 82 rotates around the cleaning roller 71 to move away from the fixed portion 81, the protrusion wall 82d of the first swivel portion 82 contacts the protrusion wall 81d of the fixed portion 81 to limit the further rotation of the first swivel portion 82. [0029] The first swivel portion 82 has an outer shape smaller than the outer shape of the fixed portion 81. Namely, the distance between the pair of side walls 82a of the first swivel portion 82 is less than the distance between the pair of side walls 81a of the fixed portion 81. Further, the distance from the cleaning roller 71 to the outer peripheral surface of the peripheral wall 82c of the first swivel portion 82 is less than the distance from the cleaning roller 71 to the inner surface of the peripheral wall 81c of the fixed portion 81. Thus, when the first swivel portion 82 rotates around the cleaning roller 71 toward the fixed portion 81, the first swivel portion 82 retracts into the fixed portion 81. Accordingly, with reference to FIG.5, at least a part of the first swivel portion 82 is accommodated inside the fixed portion 81. [0030] The second swivel portion 83 is a portion that constitutes a lower portion of the housing 74 and is rotatable relative to the fixed portion 81 and relative to the first swivel portion 82, around the rotation axis AX that is aligned with the center axis of the cleaning roller 71. The second swivel portion 83 includes a pair of side walls 83a, a lower wall 83b, and a peripheral wall 83c. The pair of side walls 83a are arranged to face each other, with the recovery chamber 74s formed therebetween in the axial direction of the cleaning roller 71. Each of the pair of side walls 83a is rotatably connected to the cleaning roller 71 and has a fan shape that increases in width in a substantially outwardly radial direction with respect to the cleaning roller 71. [0031] The lower wall 83b is connected to the lower edges of the pair of side walls 83a to cover the recovery chamber 74s from below. The blade 72 and the conveyor device 73 are fixed onto the lower wall 83b. The peripheral wall 83c forms a circumferential surface that extends substantially along an arc centered around the center axis (rotation axis AX) of the cleaning roller 71 and is connected to the pair of side walls 83a and the lower wall 83b. As shown in FIG. 4, the upper end of the peripheral wall 83c is provided with a protrusion wall 83d which protrudes in a direction pointed away from the cleaning roller 71. As shown in FIG.4, when the second swivel portion 83 rotates around the cleaning roller 71 to move away from the fixed portion 81 and the housing 74 is unfolded (or expanded), the protrusion wall 83d of the second swivel portion 83 contacts the protrusion wall 82e of the first swivel portion 82 to limit the further rotation of the second swivel portion 83. [0032] The second swivel portion 83 has an outer shape smaller than the outer shape of the first swivel portion 82. Namely, the distance between the pair of side walls 83a of the second swivel portion 83 is less than the distance between the pair of side walls 82a of the first swivel portion 82. Further, the distance from the cleaning roller 71 to the outer surface of the peripheral wall 83c of the second swivel portion 83 is less than the distance from the cleaning roller 71 to the inner surface of the peripheral wall 82c of the first swivel portion 82. Thus, when the second swivel portion 83 rotates around the cleaning roller 71 toward the fixed portion 81, the second swivel portion 83 retracts into the first swivel portion 82. Accordingly, with reference to FIG.5, at least a part of the second swivel portion 83 is accommodated inside the first swivel portion 82. [0033] As described above, the first swivel portion 82 and the second swivel portion 83 of the housing 74 are rotatable around the rotation axis AX. For example, when an external force is applied to the first swivel portion 82 and the second swivel portion 83, the first swivel portion 82 and the second swivel portion 83 rotate around the rotation axis AX toward the fixed portion 81 and the second swivel portion 83 may be moved from the operational position P1 to the retraction position P2. The operational position P1 is the lowest descending position of the second swivel portion 83. The retraction position P2 is the highest ascending position of the second swivel portion 83, corresponding to a position inside the fixed portion 81. With reference to FIG. 5, when the second swivel portion 83 moves to the retraction position P2, at least a part of the first swivel portion 82 and the second swivel portion 83 is accommodated inside the fixed portion 81, such that the housing 74 is folded (or retracted). Consequently, as shown in FIG.6, the size of the housing 74 is reduced and the volume of the recovery chamber 74s of the housing 74 is reduced in size accordingly. The housing 74 is brought into a folded state, for example, when the transfer device 30 is pulled out from the casing 15 of the image forming apparatus for the maintenance of the image forming apparatus 1, which will be described further below with reference to FIGS.7A to 7C. [0034] On the other hand, for example, when the first swivel portion 82 and the second swivel portion 83 rotate around the rotation axis AX in a direction pointed away from the fixed portion 81 due to the own weight, the position of the second swivel portion 83 moves from the retraction position P2 to the operational position P1. Accordingly, the housing 74 is unfolded as shown in FIG.3. As a result, as shown in FIG.4, the size of the housing 74 is increased so that the volume of the recovery chamber 74s of the housing 74 is increased. During the operation of the toner recovery device 70, the housing 74 is used in an unfolded state. [0035] The second swivel portion 83 of the housing 74 may be further provided with the latch 85 which allows the second swivel portion 83 to engage (or lock) with the fixed portion 81 when the second swivel portion 83 is disposed at the retraction position P2 and the housing 74 is folded. The latch 85 is formed in a substantially L shape in the side view and includes a base end portion 86, a front-end portion 87, and an extension portion 88. The base end portion 86 is fixed to the second swivel portion 83. The front-end portion 87 is located on the side opposite to the base end portion 86 and the front-end portion 87 is provided with the convex portion 87a engaging with the concave portion 81e formed in the fixed portion 81. The extension portion 88 is provided between the base end portion 86 and the front-end portion 87. The extension portion 88 functions as a leaf spring which biases the front-end portion 87 toward the side wall 81a of the fixed portion 81. [0036] Further, the image forming apparatus 1 may further include a disengagement portion 90 which is disposed adjacent to the fixed portion 81 of the housing 74 to disengage (or unlock) the engagement between the fixed portion 81 and the latch 85 of the second swivel portion 83 (cf. FIG.9A). The disengagement portion 90 is, for example, a stick-shaped or wedge-shaped elongated member and is disposed at a position inside the casing 15 to align with the fixed portion 81, namely to align with a position of the latch 85 when the second swivel portion 83 is at the retraction position P2 (e.g., in the folded state of the housing 74). When the toner recovery device 70 is disposed at an installation position, the disengagement portion 90 slides between the fixed portion 81 and the latch 85 and separates the fixed portion 81 from the second swivel portion 83, so as to disengage (or unlock) the engagement therebetween. [0037] An operation of the toner recovery device 70 will be described with reference to FIGS. 7A to 7C. During the maintenance of the image forming apparatus 1, the transfer device 30 may be extracted from the casing 15 of the image forming apparatus 1. At this time, the transfer device 30 is pulled out in the X direction indicated by an arrow in FIGS.7A, 7B, 7C. When the transfer device 30 is pulled out in the X direction, as shown in FIG. 7A, the toner recovery device 70 connected to the transfer device 30 moves in the X direction together with the transfer device 30 and the housing 74 contacts the developing device 20. When the transfer device 30 is moved further in the X direction, a contact between the developing device 20 and the housing 74 generates an upward force applied on the second swivel portion 83 so that the second swivel portion 83 rotates around the cleaning roller 71 so as to lift toward the fixed portion 81. Accordingly, as shown in FIG. 7B, the second swivel portion 83 moves upward. [0038] When the transfer device 30 is moved further in the X direction from the position shown in FIG. 7B, as shown in FIG. 7C, the upward force lifts the first swivel portion 82 and the second swivel portion 83 so that the first swivel portion 82 and the second swivel portion 83 further rotate around the cleaning roller 71. Accordingly, the first swivel portion 82 and the second swivel portion 83 are accommodated inside the fixed portion 81 and the housing 74 is folded. [0039] At this time, the latch 85 rotates in accordance with the rotation of the second swivel portion 83 and the convex portion 87a of the latch 85 moves to a position facing the concave portion 81e formed in the fixed portion 81. Then, the convex portion 87a of the latch 85 engages with the concave portion 81e due to the biasing force of the extension portion 88. Accordingly, the second swivel portion 83 is fixed to the fixed portion 81 and the housing 74 is locked in a folded state. Since the size of the housing 74 is reduced when the housing 74 is in the folded position, the interference between the toner recovery device 70 and the developing device 20 is prevented when the transfer device 30 is pulled out in the X direction. Accordingly, the transfer device 30 and the toner recovery device 70 are more easily moved out of the image forming apparatus 1, so as to facilitate maintenance of the image forming apparatus 1. [0040] With reference to FIGS. 8A and 8B, a movement of the housing 74 when the transfer device 30 and the toner recovery device 70 are installed into the image forming apparatus 1, will be described. When the transfer device 30 having been removed during the maintenance or the like, is installed inside the casing 15 of the image forming apparatus 1, the transfer device 30 is inserted in the Y direction shown in FIG. 8A. At this time, the toner recovery device 70 is inserted into the casing 15 together with the transfer device 30 while the housing 74 is folded. When the toner recovery device 70 moves to an installation position, the engagement between the fixed portion 81 and the latch 85 is disengaged by the disengagement portion 90 disposed adjacent to the installation position. [0041] For example, when the toner recovery device 70 is moved to the installation position as shown in FIG. 9A, the disengagement portion 90 is inserted between the latch 85 and the fixed portion 81 of the housing 74 and the engagement between the concave portion 81e and the convex portion 87a of the latch 85 is disengaged as shown in FIG. 9B. When the engagement between the latch 85 and the fixed portion 81 of the housing 74 is disengaged, the first swivel portion 82 and the second swivel portion 83 rotate around the cleaning roller 71 in a direction pointed away from the fixed portion 81 and the housing 74 is unfolded as shown in FIG.8B. [0042] As described above, the toner recovery device 70 of the image forming apparatus 1 includes the first swivel portion 82 and the second swivel portion 83 which rotate around the axis of the cleaning roller 71. The first swivel portion 82 and the second swivel portion 83 rotate around the rotation axis AX toward the fixed portion 81 so that at least a part of the first swivel portion 82 and at least a part of the second swivel portion 83 is accommodated inside the fixed portion 81. Accordingly, the housing 74 is folded and the size of the housing 74 is reduced. As a result, it is possible to prevent the interference between the toner recovery device 70 and the developing device 20 when the transfer device 30 is pulled out from the casing 15 of the image forming apparatus 1 and thus to improve the maintainability of the image forming apparatus 1. Further, the package size can be reduced by packing the toner recovery device 70 while the housing 74 is folded. [0043] Additionally, the housing 74 includes two swivel portions of the first swivel portion 82 and the second swivel portion 83, but the number of the swivel portions of the housing 74 may be one or three or more. Further, the housing 74 may include the swivel portion without the fixed portion 81. For example, the entire housing may be composed of one or a plurality of swivel portions. [0044] Further, the first swivel portion 82 of the housing 74 may be made of an elastic or flexible body such as vinyl or rubber and may have a structure that can be folded in a bellows shape in the circumferential direction around the rotation axis AX. In this case, since the first swivel portion 82 is folded in the circumferential direction around the rotation axis AX when an external force is applied to the first swivel portion 82 toward the fixed portion 81, the size of the housing 74 can be reduced. [0045] With reference to FIGS. 10 and 11, another example toner recovery device 170 will be described. Hereinafter, differences from the example toner recovery device 70 will be described and overlapping description may be omitted. The example toner recovery device 170 changes to an unfolded state shown in FIG. 10 (a state in which a swivel portion 182 to be described later is disposed at the operational position P1) and a folded state shown in FIG. 11 (a state in which the swivel portion 182 is disposed at the retraction position P2). [0046] As shown in FIG.10, the toner recovery device 170 includes the blade 72, the conveyor device 73, and a housing 174. The blade 72 of the toner recovery device 170 includes the contact edge portion 72a which directly contacts the intermediate transfer belt 31 and recovers residual toner particles remaining on the intermediate transfer belt 31 from the intermediate transfer belt 31. [0047] The housing 174 defines a recovery chamber 174s accommodating the toner particles recovered from the intermediate transfer belt 31. The housing 174 includes a fixed portion 181 and a swivel portion 182. The fixed portion 181 is fixed to, for example, a support body supporting both end portions of the tension roller 34. A seal member 183 which seals the recovery chamber 74s may be provided between the fixed portion 181 and the intermediate transfer belt 31. [0048] On the other hand, the swivel portion 182 is rotatably connected to the support body through a rotation shaft extending in the extension direction of the contact edge portion 72a of the blade 72. Namely, the swivel portion 182 is rotatable around the rotation axis AX extending along the contact edge portion 72a. The rotation axis AX extends in the longitudinal direction of the tension roller 34. The swivel portion 182 rotates around the rotation axis AX to move between the operational position P1 and the retraction position P2. As shown in FIG. 11, in this housing 174, the swivel portion 182 retracts around the rotation axis AX toward the fixed portion 181 and is disposed at the retraction position P2 so that the size of the housing 74 is reduced. Accordingly, the interference between the toner recovery device 170 and the developing device 20 is prevented when the transfer device 30 is pulled out from the casing 15. Thus, the transfer device 30 and the toner recovery device 170 are more easily removed so as to facilitate the maintainability of the image forming apparatus 1. [0049] Since the swivel portion 182 rotates around the rotation axis AX in a direction pointed away from the fixed portion 181 and is disposed at the operational position P1, the size of the housing 174 is increased and the toner recovery device 170 can be operated. [0050] Additionally, the image forming apparatus 1 shown in FIG. 1 includes one toner recovery device 70, but the image forming apparatus 1 may include a plurality of toner recovery devices. For example, the image forming apparatus shown in FIG.12 includes two toner recovery devices 70A and 70B. [0051] With reference to FIG. 12, the toner recovery devices 70A and 70B have a similar structure as that of the toner recovery device 70. Namely, each of the toner recovery devices 70A and 70B includes the cleaning roller 71 and the housing 74 which accommodates toner particles recovered by the cleaning roller 71. The housing 74 of each of the toner recovery devices 70A and 70B includes the fixed portion 81 which sets a fixed position relative to the cleaning roller 71, the first swivel portion 82 which is rotatable around the cleaning roller 71 relative to the fixed portion 81, and the second swivel portion 83 which is rotatable around the cleaning roller 71 relative to the fixed portion 81. [0052] As shown in FIG. 12, the toner recovery device 70A is disposed between the tension roller 34 and the idler roller 35 to recover residual toner particles remaining on the intermediate transfer belt 31. The toner recovery device 70B is disposed on the downstream side of the rotation direction of the intermediate transfer belt 31 in relation to the toner recovery device 70A and recovers residual toner particles remaining on the intermediate transfer belt 31 without having been recovered by the toner recovery device 70A. [0053] The housing 74 of the toner recovery device 70A is folded in such a manner that the first swivel portion 82 and the second swivel portion 83 rotate around the rotation axis AX toward the fixed portion 81. Similarly, the housing 74 of the toner recovery device 70B is folded in such a manner that the first swivel portion 82 and the second swivel portion 83 rotate around the rotation axis AX toward the fixed portion 81. The second swivel portion 83 of the toner recovery device 70B is provided with the latch 85 which allows the second swivel portion 83 of the toner recovery device 70B to engage with the fixed portion 81 of the toner recovery device 70A when the housing 74 of each of the toner recovery device 70A and the toner recovery device 70B is folded. The latch 85 engages the second swivel portion 83 of the toner recovery device 70B with the fixed portion 81 of the toner recovery device 70A so that the housing 74 of each of the toner recovery device 70A and the toner recovery device 70B is locked in a folded state. [0054] It should be understood that not all aspects, advantages, and features described herein are necessarily achieved or included by any one particular example and various example features disclosed herein can be appropriately combined. [0055] For example, although the example toner recovery device 70 includes the conveyor device 73, other examples may exclude the conveyor device 73. [0056] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.