Expansion box for image forming apparatus and method of assembling image forming apparatus

Abstract

An expansion box is used for an image forming apparatus including a main body part in which an image forming part is housed, and a sheet feeder cassette which is mounted to the main body part and in which sheets to be fed to the image forming part are contained. The expansion box is attached to the main body part, covers the sheet feeder cassette protruding from the main body part, and includes an opening through which a front part of the sheet feeder cassette is exposed. The image forming apparatus includes the main body part, the sheet feeder cassette and the expansion box. An assembly method of the image forming apparatus is also provided. The assembly method includes assemblage with attachment of the expansion box to the main body part and optionally a step of assemblage without attachment of the expansion box to the main body part.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an expansion box to be attached to a main body part of an image forming apparatus, the image forming apparatus to which the expansion box is attached, and a method of assembling the image forming apparatus.

[0003] 2. Description of the Related Art

[0004] There is known an image forming apparatus in which a sheet contained in a sheet feeder cassette is fed by a sheet feeding mechanism, and an image is formed on the fed sheet by image forming techniques, for example, an electrophotographic process.

[0005] Presently, various sizes of sheets are used (for example, A3, A4, A5, B4, B5, etc.). A certain image forming apparatus has such a structure that a sheet feeder cassette containing sheets is detachably attached to the image forming apparatus, the sheet feeder cassette is prepared for each of the sheet sizes, and the sheet feeder cassette is mounted to the image forming apparatus as the need arises. The size of the sheet feeder cassette typically corresponds to the size of the sheet to be contained.

[0006] In the image forming apparatus with the structure stated above, an image forming apparatus has been proposed in which when a sheet feeder cassette with a frequently used sheet size (for example, A4 size) is mounted, the front surface of the sheet feeder cassette and the front surface of a cover of the image forming apparatus form a substantially same surface, so that an improved appearance is achieved. See, for example, JP-A-2001-114426, and JP-A-10-87099.

[0007] However, as a result of continued image forming apparatus miniaturization, sheet feeder cassettes tend to protrude from the image forming apparatus, even when a sheet feeder for a common sheet size is used.

[0008] As stated above, when the sheet feeder cassette protrudes, the overall appearance of the image forming apparatus may be adversely affected. On the other hand, when a main body frame of an image forming apparatus is made large to accommodate a sheet feeder cassette in a manner such that it does not protrude, e.g., when the front surface of the main body cover is made to lie in substantially the same surface as the front surface of the sheet feeder cassette, the image forming apparatus becomes large, and the benefits of having miniaturized the image forming apparatus are lost.

[0009] While it is conceivable that two kinds of main body frames could be manufactured, e.g., large and small, to satisfy both customers who attach importance to a clean overall appearance, and customers who attach importance to minimizing the size of the overall image forming apparatus. However, in this approach, manufacturing costs are increased.

SUMMARY OF THE INVENTION

[0010] The present invention has been made in view of the above circumstances and provides an expansion box and an image forming apparatus which can satisfy, without increasing manufacturing cost, customers who attach importance to clean overall appearance and customers who attach importance to minimizing the size of the overall image forming apparatus.

[0011] According to an aspect of the present invention, an expansion box is used for an image forming apparatus that includes a main body part, in which an image forming part is housed, and a sheet feeder cassette mounted to the main body part that contains sheets to be fed to the image forming part. The expansion box, which is preferably attached to the main body part, covers the sheet feeder cassette protruding from the main body part and includes an opening through which a front part of the sheet feeder cassette is exposed.

[0012] Accordingly, when the expansion box is attached to the main body part of the image forming apparatus, since the front part of the sheet feeder cassette is exposed through the expansion box, the front surface of the expansion box and the front surface of the sheet feeder cassette may lie in substantially the same surface. Accordingly, an image forming apparatus is obtained in which the sheet feeder cassette does not protrude in an unsightly manner. The sheet feeder cassette can be attached and detached through the opening in the expansion box.

[0013] Thus, when the sheet feeder cassette protrudes from the small main body part, an improvement in appearance can be achieved by attaching the expansion box, if desired by the user. Moreover, when the expansion box is not attached, the size of the overall image forming apparatus is minimized. Thus, it is also possible to satisfy users who place primary importance on the size of the overall image forming apparatus, rather than on appearance.

[0014] Accordingly, without increasing manufacturing cost, it is possible to satisfy both customers who attach importance to a having a clean and trim appearance and customers who attach importance to minimizing the size of the overall image forming apparatus.

[0015] According to another aspect of the present invention, an expansion box is used for an image forming apparatus that preferably includes a main body part having a main body frame in which an image forming part is housed, a main body cover which covers the main body frame, and a sheet feeder cassette which is mounted to the main body part and in which sheets to be fed to the image forming part are contained. The expansion box preferably includes an expansion frame attached to the main body frame, and a front cover that covers the sheet feeder cassette protruding from the main body part. An opening through which a front part of the sheet feeder cassette is exposed is preferably provided in the front cover of the expansion box.

[0016] The front cover of the expansion box preferably covers the sheet feeder cassette protruding from the main body part. Moreover, since the front part of the sheet feeder cassette is exposed through the front cover, the front surface of the front cover and the front surface of the sheet feeder cassette lie in substantially the same surface. Accordingly, an image forming apparatus is obtained in which the sheet feeder cassette does not protrude, and the sheet feeder cassette can be attached and detached through the opening, as described herein.

[0017] Further, to increase the strength and rigidity of the expansion box, the expansion box may preferably include an expansion frame attached to the main body frame, and it may be constructed such that the front cover is attached to the expansion frame. Thus, for example, even if a person were to collide with the expansion box, it would not be easily damaged.

[0018] According to another aspect of the present invention, an image forming apparatus includes a main body part in which an image forming part is housed, a sheet feeder cassette which is attached to the main body part containing sheets to be fed to the image forming part, and an expansion box which is attached to the main body part. The expansion box preferably substantially covers the sheet feeder cassette protruding from the main body part, and includes an opening through which a front part of the sheet feeder cassette is exposed.

[0019] Since the expansion box is attached to the image forming apparatus, the image forming apparatus satisfies both customers who attach primary importance to having a clean and trim appearance and customers who attach primary importance to minimizing the overall size of the image forming apparatus.

[0020] According to another aspect of the present invention, an assembly method for an image forming apparatus is provided in which plural types of image forming apparatuses are manufactured. The method includes assembling a main body part in which an image forming part is housed, a sheet feeder cassette which is mounted to the main body part and in which sheets to be fed to the image forming part may be contained, and an expansion box which covers the sheet feeder cassette protruding from the main body part and includes an opening through which a front part of the sheet feeder cassette is exposed. If an expansion box is desired, the assembly method includes attaching the expansion box to the main body part. Alternatively, if no expansion box is desired, then the step of attaching the expansion box to the main body part is omitted.

[0021] As described above, according to the present invention, it is possible to satisfy, without substantially increasing manufacturing cost, both customers who attach primary importance to having a clean and trim appearance and customers who attach primary importance to minimizing the size of the overall image forming apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.

[0023] FIGS. 1A and 1B depict laser printers according to an embodiment of the invention, wherein FIG. 1A is a view in which an expansion box is attached, and FIG. 1B is a view in which the expansion box is not attached;

[0024] FIGS. 2A and 2B depict a laser printer according to an embodiment of the invention, wherein FIG. 2A is a view illustrating attachment of an expansion frame and a rail member, and FIG. 2B is a view illustrating a state where the expansion frame and the rail member are attached;

[0025] FIG. 3 depicts a laser printer according to an embodiment of the invention and illustrates attachment of a power switch;

[0026] FIG. 4 depicts a laser printer according to an embodiment of the invention and illustrates attachment of a front cover;

[0027] FIG. 5 depicts a laser printer according to an embodiment of the invention and illustrates mounting a process cartridge and a sheet feeder cassette; and

[0028] FIG. 6 is a view schematically showing the inside of the laser printer according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

[0030] FIG. 1A depicts a laser printer 10 in which an expansion box 100 of the invention is attached to a printer main body 12. FIG. 1B illustrates a laser printer 11 in which expansion box 100 of the invention is not attached to the printer main body 12.

[0031] The printer main body 12 forms an image (e.g., a toner image) on the basis of image information input from an external device by well-known electrophotographic processes, and records the image on a sheet or the like. The electrophotographic process includes a series of steps in which a toner image is formed on a photosensitive body through the charging of the electrophotographic photosensitive body. An electrostatic latent image is formed by exposure, developed by toner, and transferred to a sheet, where it is heated and fixed so that the image is recorded on the sheet.

[0032] FIG. 6 is a view schematically illustrating the inside of the laser printers 10 and 11. Sheet feeder cassettes 60 are mounted to the printer main body 12 in upper and lower stages. In FIG. 6, the oblique lines indicate the optional presence of expansion box 100. As illustrated, the printer main body 12 includes an image forming part 300 for forming an image on a sheet P. The image forming part 300 includes a process cartridge 20, a transfer roller 28, an optical scanner 30, a fixing device 40, conveyance rollers 34, and a sheet exhaust roller 46.

[0033] The image forming process performed by the image forming part 300 will now be described. The process cartridge 20 includes therein a photosensitive body 22, and a part thereof is exposed from the process cartridge 20. Charging roller 24, developing unit 25 including a developing roller 26, and waste toner case 19 including a cleaning blade 18 are disposed around the photosensitive body 22. Toner case 21 is connected to the developing unit 25, and toner is supplied from the toner case 21 to the developing unit 25.

[0034] Transfer roller 28 is in contact with the photosensitive body 22 exposed from the process cartridge 20. Laser light L emitted from the optical scanner 30 passes through a gap bored in the process cartridge 20, scanning and thereby forming an image on the photosensitive body 22.

[0035] The photosensitive body 22 is rotated by a driving mechanism (not-shown), and the surface of the photosensitive body 22 is uniformly charged by the charging roller 24. Next, by the optical scanner 30, the laser light L forms the image on the surface of the photosensitive body 22, scanning it in accordance with the input data so that an electrostatic latent image, corresponding to the desired printed image, is formed on the surface of the photosensitive body 22. The electrostatic latent image is then developed by the toner on the developing roller 26, and a toner image is formed on the surface of the photosensitive body 22. Next, the toner image is moved to the transfer roller 28.

[0036] Sheets P, contained in the sheet feeder cassette 60 at either one of the upper stage or lower stage, are taken out one by one by a pickup roller 32, and sent to the conveyance rollers 34. The conveyance rollers 34 then convey each sheet P to the transfer roller 28.

[0037] With respect to each sheet P conveyed to the transfer roller 28, the toner image on the surface of the photosensitive body 22 is transferred to the sheet P by the transfer roller 28. The sheet P on which the toner image is transferred is then conveyed to the fixing device 40, and held and conveyed by a heat roller 42 and a pressure roller 44, so that the toner image is fixed to the sheet P by heat and pressure. After the fixation process is complete, the sheet P is removed by the sheet exhaust roller 46 and is stacked on a sheet exhaust tray 50. Any toner not transferred to the sheet P by the transfer roller 28 and remaining on the surface of the photosensitive body 22 is scraped away by the cleaning blade 18 and stored in the waste toner case 19.

[0038] Also as shown in FIG. 5, the process cartridge 20 is detachably attached to the printer main body 12 by opening the sheet exhaust tray 50. When the toner in the toner case 20 is exhausted, it can be exchanged with a new process cartridge 20.

[0039] The sheet feeder cassette 60 is also detachably attached to the printer main body 12. Accordingly, when the sheets P run out, the sheet feeder cassette 60 is taken out and sheets P can be re-supplied to the sheet feeder cassette 60. Thus, the sheet P supply operation is easy to perform.

[0040] A sheet feeder cassette with a size corresponding to each sheet size is preferably prepared for every sheet size (for example, A3, A4, A5, B4, B5, etc.), and the sheet feeder cassette of each sheet can be mounted in the printer main body 12 as the need arises. The sheet feeder cassette 60 preferably contains sheets P having a normally used sheet size (for example, A4 size), and has a size proportional to the size of the sheet P.

[0041] In the laser printer 10, expansion box 100 is attached to the printer main body 12, as shown in FIG. 1A and FIG. 6. Although the sheet feeder cassette 60 protrudes from the printer main body 12, a front surface 110A of the expansion box 100 and a front surface 60A of the sheet feeder cassette 60 may lie in substantially the same surface. Thus, the front surface of the laser printer 10 becomes substantially flat, providing a pleasing clean and trim overall appearance.

[0042] On the other hand, in the laser printer 11, expansion box 100 is not attached to the printer main body 12, as shown in FIG. 1B and FIG. 6. In this embodiment, since the expansion box 100 is not attached, the sheet feeder cassette 60 protrudes from the printer main body 12, and the front surface of the laser printer 11 is not flat. However, since the expansion box 100 is not attached, the overall size of the laser printer 11 is minimized.

[0043] Next, the details of the expansion box 100 and the laser printer 10 to which the expansion box 100 is preferably attached will be described. As shown in FIG. 2A, a main body frame 14, preferably made of a metal sheet or the like, is attached to a base 16. The image forming part 300 and associated components are attached to the main body frame 14. Expansion frames 102, preferably box-shaped and made of metal sheets or the like, are attached to both sides of the front surface of the main body frame 14. Rail members 104 along which the sheet feeder cassette 60 (see FIG. 5) slides are preferably attached to the inside surfaces.

[0044] FIG. 2B illustrates an embodiment in which the expansion frames 102 and the rail members 104 are attached. The rail members 104 are preferably firmly fixed to both the main body frame 14 and to the expansion frames 102 by screws or other fasteners. When the sheet feeder cassette 60 (depicted in FIG. 5) slides on the rails (e.g., to attach or detach the sheet feeder cassette 60) the rail members 104 do not rattle and the sheet feeder cassette 60 can be attached and detached in a stable manner.

[0045] In an embodiment, each of the left and right rail members 104 is fixed to both the main body frame 14 and the expansion frame 102. Separate short rail members (not shown) may optionally be individually attached to the main body frame 14 and to the expansion frame 102.

[0046] As shown in FIG. 3, in a preferred embodiment, a power switch 124 is attached to a switch fixing port 120 located in the front of the expansion frame 102. Connector 126 may be attached to a tip of a wiring cord 128 and connected to power switch 124. The wiring cord 128 is preferably made to pass through a harness 130 and is connected to a power supply (not shown) in the inside of the printer main body 12.

[0047] As illustrated in FIG. 4, a front cover 110 is preferably attached to the front surfaces of the expansion frames 102. In an embodiment, pawls 106 and 107 are formed at the rear surface of the front cover 110. The pawls 106 and 107 may be inserted in pawl fixing ports 105 and 109 of the expansion frames 102, where the tip parts 106A and 107A of the pawls 106 and 107 are retained, so that the front cover 110 is easily mounted to the expansion frames 102.

[0048] A cassette port 108, through which only the front part of the foregoing sheet feeder cassette 60 is exposed, is preferably formed in the front surface 110A of the front cover 110. In an embodiment, the sheet feeder cassette 60 can be attached and detached through this cassette port 108. Since, in a preferred embodiment, only the front part of the sheet feeder cassette 60 is exposed through the cassette port 108, the front surface 110A of the front cover 110 and the front surface 60A of the sheet feeder cassette 60 lie in substantially the same surface. In this embodiment, the front surface of the laser printer 10 appears to become substantially flat (see FIG. 1A).

[0049] Switch port 140 is preferably bored in the front cover 110 at a position corresponding to the foregoing power switch 124, and the power switch 124 is exposed through this switch port 140. Vent port 202 may be formed at the side part of the front cover 110. Thus, a space 204 (see FIG. 4) surrounded by the front cover 110 and the expansion frame 102 may function as a duct for performing air intake and/or air exhaustion from holes 210 or the like formed in the main body frame 14 and connecting to the inside of the printer main body 12.

[0050] Expansion frames 102 and the front cover 110 are preferably not made as separate bodies. Expansion frames 102 and the front cover 110 may be integrally molded to promote the efficiency of the attachment operation.

[0051] As shown in FIG. 5, a side cover 112 and an upper cover 114 are attached, and when the process cartridge 20 and the sheet feeder cassette 60 are mounted, the laser printer 10 to which the expansion box 100 is attached is completed.

[0052] Upper cover 114 is preferably constructed to cover not only the printer main body 12 but also the expansion box 100. Vent holes 200 are preferably also formed in the side cover 112, and the air intake and/or air exhaustion can be performed via vent hole 200.

[0053] Next, the operation of a laser printer 10 according to aspects of the present invention will be described. As shown in FIG. 1A, in the laser printer 10, the sheet feeder cassette 60 does not appear to protrude from the laser printer 10 due to the presence of the expansion box 100 (the expansion frames 102 and the front cover 110), making the front surface of the laser printer 10 appear to be substantially flat. Thus, the laser printer 10 has an attractive clean and trim appearance.

[0054] As described above, the expansion box 100 preferably includes expansion frames 102 attached to the main body frame 14, and the front cover 110 is preferably attached to the expansion frames 102 (see FIGS. 2 and 4). Since the expansion frames 102 are preferably made of metal sheets or any material having sufficiently high strength, the strength of the expansion box 100 is also sufficiently high. Thus, for example, even if a person were to accidentally collide with the expansion box 100, it would not be easily damaged.

[0055] Moreover, since the expansion frames 102 have sufficient strength, as described above, the rail members 104 (see FIGS. 2A and 2B) can be attached. Thus, the sheet feeder cassette 60 preferably slides in to the expansion box 100. Accordingly, operability at the time of attachment and/or detachment of the sheet feeder cassette 60 is not impaired.

[0056] The power switch 124 is preferably exposed through the front surface 110A of the front cover 110 and may be disposed at the front surface of the laser printer 10. Accordingly, operability is not impaired. In this embodiment, in addition to the power switch 124, other operational devices, for example, a control panel 250 may be attached.

[0057] Further, as described above, since the expansion box 100 may also function as a duct (the space 204 surrounded by the front cover 110 and the expansion frames 102 (see FIG. 4)), the air intake and/or air exhaustion of the printer main body 12 can be performed more efficiently.

[0058] Next, the laser printer 11 without the optional expansion box 100 attached will be described. As shown in FIG. 1B, a front cover 160, side covers 112, an upper cover 164, and rail members (not shown) are attached to the main body frame 14 shown in FIG. 2A. Process cartridge 20 and sheet feeder cassette 60 are mounted as illustrated, forming the laser printer 11 without expansion box 100 attached.

[0059] In laser printer 11, the upper cover 164 covers only the upper part of the main body frame 14, different from the upper cover 114 of the laser printer 10. Moreover, as shown in FIG. 3, the power switch 124 is preferably attached to the switch fixing port 122 formed in the front of the main body frame 14.

[0060] Although not shown, in the case of the laser printer 11 (without expansion box 100), the base 16 shown in FIG. 12A has a length preferably not exceeding dotted line D so that it is received within the main body frame 14. Similarly, the rail member is also short so that it may be received within the main body frame 14.

[0061] Next, the operation of the laser printer 11 will be described. As shown in FIG. 1B, in the laser printer 11, the sheet feeder cassette 60 protrudes from the printer main body 12, and the front surface of the laser printer 11 is not flat. However, since the expansion box 100 is not attached, the overall laser printer 11 is small in size.

[0062] As described previously, the primary difference between laser printer 10 and the laser printer 11 is whether or not expansion box 100 is attached to the printer main body 12 (see FIGS. 1A and 1B). Thus, two configurations of laser printers 10 and 11 can be produced at low cost, i.e., the laser printer 10 in which the expansion box 100 is attached, and the laser printer 11 in which the expansion box 100 is not attached.

[0063] Accordingly, in accordance with embodiments of the invention, advances in miniaturization of the printer main body 12 may satisfy the needs of customers whose primary interest is in minimizing the size of the printer. On the other hand, customers for whom aesthetics are paramount can also be satisfied without impairing operability of the printer, sheet feeder, power switch, or the like, by attaching the expansion box 100, thereby providing a clean, trim appearance by concealing the sheet feeder cassette 60, which protrudes from the printer main body 12.

[0064] As previously discussed, although it is conceivable that different size frames could be used, e.g., a large main body frame to conceal the front surface 60A of the sheet feed box 60, to satisfy customers who attach primary importance to aesthetics, manufacturing two sizes of frames causes manufacturing costs to become too high.

[0065] However, in accordance with the presently disclosed embodiments, it is possible to satisfy, without increasing the cost, both types of customers with a single apparatus. Of course, although a laser printer 10 has been used as an example of an image forming apparatus to illustrate embodiments of the invention, the invention is not limited to a laser printer. For example, embodiments of the invention may be applied to any other image forming apparatus, such as copy machines, facsimile machines, compound copy and facsimile machines, and any other similar machine having a cartridge extending therefrom.

[0066] Other preferred embodiments of the present invention are described below. In the expansion box of the present invention, the rail member along which the sheet feeder cassette slides may be attached to the expansion frame. In the above expansion box, the rail member along which the sheet feeder cassette slides may be attached to the expansion frame. Thus, since the sheet feeder cassette slides into the expansion box, it can be easily attached and/or detached. Accordingly, the operability of the sheet feeder cassette is not impaired.

[0067] In the expansion box of the present invention, operational devices such as a power switch may be attached to the expansion frame. Moreover, a port through which the operational device is exposed may be formed in the front cover. Accordingly, even if the expansion box is attached, operability of the device is not impaired. Space savings of the main body part can also be attained by attaching operational devices, such as a power switch, to the expansion frame.

[0068] In the expansion box according to embodiments of the present invention, one or more vent holes may be formed in the front cover, and the space surrounded by the front cover and the expansion frame may function as a duct.

[0069] In embodiments of the above expansion box, a vent hole is formed in the front cover, and the space formed by the front cover and the expansion frame functions as the duct. Accordingly, when the expansion box is attached, air intake and/or exhaust to or from the inside of the main body can be efficiently performed. Since there are many cavity portions in the space surrounded by the front cover and the expansion frame, the flow of air is good, and the space is suitable as a duct.

[0070] While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but have the full scope defined by the language of the following claims, and equivalents thereof.

[0071] The entire disclosure of Japanese Patent Application No. 2003-335189 filed on Sep. 26, 2003 including specification, claims, drawings and abstract is incorporated herein by reference in its entirety.

Claims

What is claimed is:

1. An image forming apparatus comprising: a main body part including an image forming part; a sheet feeder cassette removably attachable to the main body part and at least partially extending therefrom when fully attached to the main body part; an expansion box attachable to the main body part, the expansion box covering the portion of the sheet feeder cassette that at least partially extends from the main body part, the expansion box including an opening through which at least a portion of the front part of the sheet feeder cassette is exposed.

2. The image forming apparatus according to claim 1, wherein the main body part comprises a main body frame in which the image forming part is housed and a main body cover which substantially covers the main body frame.

3. The image forming apparatus according to claim 2, wherein the expansion box is attachable to the main body cover.

4. The image forming apparatus according to claim 2, wherein the expansion box is attachable to the main body frame.

5. The image forming apparatus according to claim 1, wherein the expansion box includes a port for exposing an operational device.

6. The image forming apparatus according to claim 5, wherein the operational device is a power switch.

7. The image forming apparatus according to claim 5, wherein the operational device is a control panel.

8. An expansion box for an image forming apparatus, the expansion box comprising: an expansion frame attachable to the image forming apparatus; and a front cover which substantially covers the sheet feeder cassette protruding from the main body part, the front cover including opening through which at least a portion of the front part of the sheet feeder cassette is exposed.

9. The expansion box according to claim 8, further comprising an expansion frame attachable to a frame of the main body of the image forming apparatus.

10. The expansion box according to claim 9, wherein the expansion frame is attachable to a rail member along which the sheet feeder cassette slides.

11. The expansion box according to claim 9, wherein an operational device is attached to the expansion frame, and the front cover includes a port through which the operational device is exposed.

12. The expansion box according to claim 11, wherein the operational device is a power switch.

13. The expansion box according to claim 11, wherein the operational device is a control panel.

14. The expansion box according to claim 9, wherein an operational device is attached directly to the front cover.

15. The expansion box according to claim 8, wherein the front cover includes a vent hole, and a space surrounded by the front cover and the expansion frame functions as an air duct.

16. An image forming apparatus comprising: a main body part in which an image forming part is housed; a sheet feeder cassette which is attachable to the main body part for containing sheets to be fed to the image forming part; and an expansion box which is attachable to the main body part, the expansion box substantially covering the sheet feeder cassette protruding from the main body part, and including an opening through which at least a front part of the sheet feeder cassette is exposed, wherein the front part of the sheet feeder cassette and at least one surface of the expansion box lie in substantially the same plane.

17. A method of assembling plural types of image forming apparatuses comprising: assembling a main body part in which an image forming part is housed; providing a sheet feeder cassette capable of being mounted to the main body part; providing an expansion box capable of substantially concealing the sheet feeder cassette protruding from the main body part, the expansion box including an opening through which a front part of the sheet feeder cassette is at least partially exposed; selecting whether to attach the expansion box to the main body part according to whether an expansion box is desired in the finished apparatus or not.