KR20070024217A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus is provided to provide an open/close structure of an upper cover, thereby maintaining uniform locking force regardless of a use time and easily adjusting locking force according to use purpose. An image forming apparatus for forming an image on a print medium comprises a main body and a pivotable upper cover(204,206) mounted to the main body. A cam unit(215a) is installed around a pivotable axis of the upper cover(204,206). A cam protrusion is formed on the cam unit(215a). A bushing unit(215b) on which the cam unit(215a) sits and is vertically moved according to rotation of the cam unit(215a). A spring unit(215d) installed to the main body closely adheres the bushing unit(215b) to the cam unit(215a). The spring unit(215d) shrinks or elongates according to vertical movement of the bushing unit(215b).

Description

Image forming apparatus

1 is a partial perspective view illustrating an opening and closing structure of an upper cover part in a conventional image forming apparatus.

2 is a perspective view schematically showing an image forming apparatus according to a preferred embodiment of the present invention.

3 is a perspective view illustrating a state in which the second upper cover part is opened in the image forming apparatus of FIG. 1.

4 is a side cross-sectional view schematically illustrating the image forming apparatus of FIG. 1.

FIG. 5A is a side cross-sectional view schematically illustrating an enlarged portion A of FIG. 4, where a printing job is normally performed.

5B and 5C are side cross-sectional views schematically illustrating an enlarged portion A of FIG. 4, and shows a step by step process in which the second upper cover part is opened due to a jam of a print medium during a printing operation.

6 is an exploded perspective view illustrating an opening and closing structure of a second upper cover part in the image forming apparatus of FIG. 1.

FIG. 7 is a partial cutaway sectional view taken along the line VII-VII of FIG. 6. FIG.

<Explanation of symbols for the main parts of the drawings>

200: image forming apparatus 201: main body

202: discharge tray 204: first upper cover portion

205a and 205b: Paper feed cassette 206: second upper cover part

207: first lower cover portion 208: second lower cover portion

209: guide claw 215: opening and closing structure of the second upper cover portion

276: heat roller 277: pressure roller

278: decal unit, discharge roller 280: pickup unit

298: cleaning unit

The present invention relates to an image forming apparatus, and more particularly, having an opening and closing structure of an upper cover part capable of maintaining a constant locking force regardless of a period of use and easily adjusting the locking force according to the purpose of use. An image forming apparatus.

In general, the image forming apparatus includes a paper feeding unit, an exposure unit, a developing unit, a transfer unit, a fixing unit, and a discharge unit.

Here, the paper feeding unit feeds the print medium into the chemical conversion apparatus, the exposure unit forms an electrostatic latent image on the surface of the photoconductor, and the developing unit supplies a toner, which is a developer, to the electrostatic latent image formed on the surface of the photoconductor, thereby replacing the electrostatic latent image with the toner image. Develop.

The fixing unit includes a heat roller and a pressure roller, and applies high heat and high pressure to the printing medium to which the toner image is attached to melt and fix the toner image to the printing medium passing through the fixing unit. On the other hand, the fixing unit uses high temperature and high pressure to fix the toner image, so that the print medium is flexible. For this or other reasons, the print media is entangled in the hitler and begins to wind around when discharged through the fuser nip, so-called accordion jam or accordion effect. Print media jams).

In order to detect such a print media jam, an exit sensor has been generally installed between the fixing unit nip and the discharge roller described later.

The discharge unit includes a discharge roller and discharges the print medium on which the fixing is completed, out of the image forming apparatus.

1 is a partial perspective view illustrating an opening and closing structure of an upper cover part in a conventional image forming apparatus. Referring to the drawings, a conventional image forming apparatus includes an upper cover part, and the upper cover part is typically formed by being divided into a first upper cover part 104 and a second upper cover part 206. In addition, the second upper cover part 206 is coupled to the first upper cover part 104 so as to be openable and closeable.

That is, the hooking jaw 104a is formed in the first upper cover part 104, and the hook 106a is formed in the second upper cover part 106, and when the second upper cover part 106 is closed, the second upper cover part 104 is closed. The hook 106a of the upper cover portion is directed downwardly to the engaging jaw 104a of the first upper cover portion 104. Thereafter, the hook 106a protrudes into the locking jaw 104a on the basis of the vertical line connecting the upper side and the lower side, whereby the pressure for pushing the second upper cover portion 106 upward is a predetermined reference value. If it is within the second upper cover portion 106 is not opened. However, when the pressure for pushing the second upper cover portion 106 upwards is higher than a predetermined reference value, the hook 106a may move beyond the locking jaw 104a and rise above the locking jaw 104a. The two upper cover parts 106 are opened.

However, as in the case where the conveying path of the print medium has a so-called C-path feeding structure having a C shape, such as when the fixing unit is installed directly under the second upper cover portion, A large amount of heat is transferred to the second upper cover part. Therefore, in such a case, when the image forming apparatus is used for a long time, the hook 106a illustrated in FIG. 1 is thermally deformed, thereby reducing a portion of the hooking jaw 104a of the first upper cover portion 104. Therefore, the locking force caused by the engagement of these hooks 106a and the locking step 104a is also reduced.

In addition, when the hook 106a is thermally deformed as described above, when the process of opening and closing the second upper cover portion 106 is repeated, the hook 106a and the locking jaw 104a are worn and these hooks 106a are worn. And locking force due to the coupling of the locking step 104a may be lowered.

When the locking force is lowered in the opening and closing structure of the upper cover part as described above, even when the print media jam does not occur in the structure without the exit sensor, for example, even when the thickness of the print media is thick, There is a problem that a malfunction occurs in opening the second upper cover. As such, when the second upper cover part is opened, the image forming apparatus recognizes that a print media jam occurs unconditionally and stops the print job, thereby causing a lot of inconvenience to the user.

An object of the present invention is to provide an image forming apparatus having an opening and closing structure of an upper cover portion capable of maintaining a constant locking force regardless of a period of use.

Still another object of the present invention is to provide an image forming apparatus having an opening and closing structure of an upper cover portion which can easily adjust a locking force according to an intended use.

According to the present invention, an image forming apparatus having an image formed on a printing medium and including a main body and an upper cover part rotatably installed on the main body, wherein the cam protrusion is formed around the rotating shaft of the upper cover part. A cam portion, a bushing in which the cam portion is seated and vertically move up and down according to the rotation of the cam portion, and installed in the main body and contracted or elastically restored according to the vertical movement of the bushing portion, and the bushing portion is formed in the cam portion. There is provided an image forming apparatus having an upper cover part opening and closing structure including a spring part in close contact with the upper part.

According to an embodiment of the present invention, the upper cover part opening and closing structure further includes a bushing part guide installed in the main body to guide vertical movement of the bushing part and having guide ribs formed thereon.

According to a preferred embodiment of the present invention, the bushing portion is formed with a first groove accommodating the cam protrusion, a locking jaw pressed by the cam protrusion, and a second groove accommodating the guide rib of the bushing portion guide. .

According to another embodiment of the present invention, when a jamming phenomenon occurs in the print medium on the conveyance path, the contact with the print medium is opened upward when the pressure of the print medium increases due to the jamming phenomenon of the print medium. The lower cover part is further formed so that the upper cover part is opened to contact the lower cover part when the lower cover part is opened.

According to a preferred embodiment of the present invention, the upper cover part is formed to include a first upper cover part and a second upper cover part, and the first upper cover part is fixed to the main body and is formed to open and close only the second upper cover part. .

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

2 is a perspective view schematically illustrating an image forming apparatus according to a preferred embodiment of the present invention, and FIG. 3 is a perspective view illustrating a state where the second upper cover part is opened in the image forming apparatus of FIG. 1.

2 and 3, an image forming apparatus 200 according to an exemplary embodiment of the present invention includes a main body 201, top cover portions 204 and 206, discharge stage 202, and bottom cover portion 207. 208, pressure roller 277, heat roller 276, guide claw 209 and rollers 278.

Here, the upper cover parts 204 and 206 are disposed above the main body 201 and include a first upper cover part 204 and a second upper cover part 206. At this time, the first upper cover portion 204 is fixed to the main body 201 and the second upper cover portion 206 is coupled to the first upper cover portion 204 and at least two parts, specifically one end of the A portion and a portion of the other end corresponding thereto are rotatably coupled. The remaining portions of the ends of the second upper cover portion 206 are not coupled with the first upper cover portion 204 and are simply placed thereon.

The discharge stage 202 is disposed on the first upper cover portion 204.

The pressure roller 277 and the heat roller 276 are disposed to face each other in the axial direction, and the guide claw 209 is disposed on the outer circumferential surface of the heat roller 276 so as to be in contact with each other.

The discharge stage 202 and the guide claw 209 will be described later.

Rollers 278 are disposed above the guide claw 209, and these rollers 278 simultaneously serve as a decal unit and a discharge roller, which will be described later.

Lower cover parts 207 and 208 are disposed below the upper cover parts 204 and 206 to cover the pressure roller 277, the heat roller 276 and the guide claw 209. Here, the lower cover parts 207 and 208 are formed to include the first lower cover part 207 and the second lower cover part 208, and the second lower cover part 208 is the first lower cover part 207. ) And at least two portions are combined, and specifically, a portion of one end and a portion of the other end corresponding thereto are rotatably coupled. However, the present invention is not limited thereto, and the lower cover parts 207 and 208 may be integrally formed. In addition, the remaining portions of the ends of the second lower cover portion 208 may be coupled to the first lower cover portion 207 by a hook method or the like, and are not simply coupled to the first lower cover portion 207, but thereon. It may be on the floor.

4 is a side cross-sectional view schematically illustrating the image forming apparatus of FIG. 1.

Referring to FIG. 4, an image forming apparatus 200 according to an exemplary embodiment of the present invention includes a main body 201, an exposure part 210, a developing part 220, and a photosensitive member provided inside the main body 201. 230, a cleaning member 238, and a charging roller 239.

Here, the exposure unit 210 scans the light corresponding to the image information to the photosensitive member 230 to be described later according to the image signal so that the electrostatic latent image is formed on the outer circumferential surface of the photosensitive member 230. In addition, the exposure unit 210 includes a light source (not shown) for scanning the laser beam, and a beam deflector for deflecting the laser beam irradiated from the light source.

The developing unit 220 is a cartridge type detachably mounted inside the main body 201, and includes a developing unit housing 222 forming an exterior, a developing roller 240, a toner layer restricting unit 250, and a supply therein. The roller 260 and an agitator 262 are installed. Also, a toner supply unit 225 for accommodating toner as a developer is provided inside the developing unit housing 222. In addition, a door 203 is provided at an upper side of the main body 201 to allow the developing unit 220 to enter and exit the main body 201.

The developing roller 240 attaches the toner contained in the housing 222 to its outer circumference and supplies the toner to the photosensitive member 230. In addition, the developing roller 240 accommodates the solid powder toner, and supplies these toners to the electrostatic latent image formed on the photosensitive member 230 to develop the toner image. In addition, a developing bias voltage is applied to the developing roller 240 for supplying these toners to the photosensitive member 230.

The supply roller 260 supplies the toner so that the toner is attached to the developing roller 240.

The stirrer 262 agitates the toner at a predetermined speed so that the toner in the toner supply unit 225 does not harden, and transports the toner toward the feed roller 260.

The toner layer regulating unit 250 is fixed at one side to the housing 222 and at the other side to contact the developing roller 240 to regulate the height of the toner attached to the outer circumferential surface of the developing roller 240, and toner to a predetermined polarity. Triboelectrically charged.

The photosensitive member 230 is charged to a predetermined potential by the charging roller 239, and an electrostatic latent image corresponding to the image to be printed by the light irradiated from the exposure unit 210 is formed on the outer circumferential surface thereof according to the image signal. The outer circumferential surface exposed to the outer circumference of the photosensitive member 230 faces the transfer roller 270.

A charging bias voltage is applied to the charging roller 239 to charge the outer circumference of the photosensitive member 230 to a uniform potential. Instead of the charging roller 239, a corona discharger (not shown) may be employed.

The cleaning member 238 is installed in the housing 232 provided with the waste toner storage 236, and one end of the cleaning member 238 contacts the photosensitive member 230 with a predetermined pressure to scrape off the toner remaining in the photosensitive member 230. One side edge portion of the cleaning member 238 may be installed in the support member 237 that is separately installed in the housing 232. The other edge portion of the cleaning member 238 contacts the photosensitive member 230 with a predetermined pressure to scrape the toner remaining in the photosensitive member 230 after the transfer.

The toner separated from the photosensitive member 230 by the cleaning member 238 is stored in the waste toner storage unit 236.

The transfer roller 270 is installed to face the outer circumferential surface of the photosensitive member 230, and a transfer bias voltage having a polarity opposite to that of the toner image is applied so that the developed toner image is transferred to the print medium P. The toner image is transferred to the print medium P by the electrostatic force acting between the photosensitive member 230 and the transfer roller 270. Here, the toner image developed on the outer circumferential surface of the photosensitive member 230 is transferred to the printing medium P passing between the transfer roller 270 and the photosensitive member 230 by the contact pressure between the photosensitive member 230 and the transfer roller 270. It may be transferred.

The fixing unit 275 includes a heat roller 276 and a pressure roller 277 installed to face the heat roller 276. The fixing unit 275 applies heat and pressure to the toner image transferred to the print medium P to print the toner image to the print medium P. To settle in. Here, the heat roller 276 is provided so as to be opposed to the pressure roller 277 in the axial direction as a heat source for permanently fixing the toner image. Here, the pressure roller 277 is installed to face the heat roller 276 to apply a high pressure to the print medium P to fix the toner image to the print medium P.

The decal part 278 removes curl of the print medium P in which curl is generated by heat while passing through the fixing unit 275.

The discharge roller 278 discharges the print medium P on which the fixing is completed, out of the image forming apparatus 200. The print medium P discharged from the image forming apparatus 200 is loaded on the discharge table 202. In this embodiment, the discharge roller 278 is configured to perform the role of the decal unit 278 at the same time. That is, the discharge roller 278 and the decal part 278 are integrated.

In addition, the image forming apparatus 200 includes first and second paper feed cassettes 205a and 205b provided below the main body 201 and on which the print medium P is loaded. Here, the image forming apparatus 200 may include only one of the first paper feed cassette 205a and the second paper feed cassette 205b.

The pickup units 280 and 282 pick up the loaded print media P one by one and take out them.

The conveying roller 281 provides a conveying force for conveying the picked up print medium P to the print media aligner 290 side. Here, the print media aligner 290 may print the toner image on the desired portion of the print medium P before the print medium P passes between the photosensitive member 230 and the transfer roller 270. Align (P).

5A is a side cross-sectional view schematically showing an enlarged portion A of FIG. 4, and a printing operation is normally performed. FIGS. 5B and 5C are enlarged side cross-sectional views schematically showing an enlarged portion A of FIG. 4. A process of jamming the print media occurs during operation to show the step of opening the second upper cover part step by step. FIG. 6 is an exploded perspective view illustrating an opening and closing structure of the second upper cover part in the image forming apparatus of FIG. 1. Fig. 6 is a partial cutaway sectional view taken along the line VIII-VIII.

First, look at the arrangement and the operation of the components shown in Figure 5a as follows.

The pressure roller 277 and the heat roller 276 are disposed to face each other with respect to the axial direction, and the guide claw 209 is disposed on the outer circumferential surface of the heat roller 276 so as to be in contact with each other.

In addition, rollers 278 are disposed above the guide claw 209, and the second lower cover part 208 is disposed at the same or similar height as the rollers 278. Here, the second lower cover portion 208 is rotatably coupled to the first lower cover portion 207, the first lower cover portion 207 is the pressure roller 277 and all the rollers on the side end surface 276 and most of the second lower cover portion 208 are disposed to cover. In addition, the second lower cover part 208 is closed because the printing operation is normally performed.

In addition, a first upper cover part 204 and a second upper cover part 206 are disposed above the second lower cover part 208.

In addition, a second upper cover part opening and closing structure 215 is provided below the second upper cover part 206. The second upper cover part opening and closing structure 215 includes a cam part 215a, a bushing part, and a bushing part. 215b), the bushing part guide 215c and the spring part 215d are preferably included. However, the present invention is not limited thereto, and the second upper cover part opening and closing structure 215 may be variously modified.

Here, the cam portion 215a is provided in the second upper cover portion 206, and the cam protrusion 215a 'is formed on the outer circumferential surface of the cam portion 215a in parallel with the rotational direction of the cam portion 215a.

In addition, the bushing part 215b is a place where the cam part 215a is seated and vertically moves up and down by the action of the cam protrusion 215a 'as the cam part 215a is rotated. As illustrated in FIG. 6, the bushing part 215b includes a first groove A for accommodating the cam protrusion 215a ', a locking jaw B pressed by the cam protrusion 215a', and a bushing described later. The second groove C receiving the guide rib 215c 'of the sub guide 215c and the protrusion D inserted into the center space of the spring portion 215d are formed. In FIG. 5A, the cam protrusion 215a ′ is horizontally covered with the latching jaw B of the bushing portion 215b since the printing operation is normally performed and the second upper cover portion 206 is closed.

In this case, the bushing part guide 215c is installed in the main body 201, and guide ribs 215c 'are formed to guide the vertical movement of the bushing part 215b.

In addition, the spring portion 215d is installed in the main body 201 and contracted or elastically restored according to the vertical movement of the bushing portion 215b, and serves to bring the bushing portion 215b into close contact with the cam portion 215a. In FIG. 5A, the spring portion 215a is in an initial state not contracted or extended.

Meanwhile, as shown in the drawing, the printing medium P exits the nip of the fixing unit 275 between the pressure roller 277 and the heat roller 276, and then is driven by the guide claw 209. It is separated from the 276 is discharged to the outside through the roller 278.

The image forming apparatus according to the present invention is not limited to the above-described configuration, and various other configurations are possible as long as the same purpose can be achieved.

Next, the arrangement of the components shown in FIGS. 5B and 5C and the operation thereof will be described.

In the drawings, when the print media jams such as the accordion effect occurs on the transport path, it is shown schematically how the components work to stop the print job. In this case, the accordion effect means that the jamming phenomenon of the print medium P occurs in the image forming apparatus, so that the print medium P is folded and wrinkled like an accordion, and the heat roller 276 and the pressure roller 277 are connected to each other. It usually occurs in the space between the fixing unit 275 and the second lower cover portion 208 including.

Once the print media is jammed in the predetermined print media P, the print media may be sequentially jammed in other print media P transferred along the transfer path.

When the print media jam occurs as described above, in particular, in the discharge structure without the exit sensor, when the pressure of the print media P is higher than a predetermined reference value, the second lower cover portion 208 is opened. Then, the second lower cover portion 208 is opened by the second upper cover portion 206 in order to stop printing. In this case, when the second lower cover portion and the second upper cover portion are conventionally coupled to the first lower cover portion and the first upper cover portion so as to be openable and closed, the coupling portions may have a pressure higher than a predetermined reference value. It is designed to have a locking force to open. However, in the structure in which the fixing unit is installed directly under the cover parts, the coupling units are heat-deformed by heat generated in the fixing unit, or wear and tear as the opening / closing operation is repeated, thereby weakening the bonding force. Even when lower than the standard value of these coupling parts are released by the combination is a problem that the printing operation is stopped.

On the other hand, when a plurality of print media (P) is tangled in the area where the jamming phenomenon of the print media occurs without being discharged to the outside, the guide claw (P) is disposed in the vicinity of the heat roller 276 ( 209 is pressed, the guide claw 209 in succession to press the heat roller 276 causes damage to the heat roller 276, such as scratches. In addition, when the jamming phenomenon of the print media occurs in succession to the plurality of print media P as described above, the print media P is entangled with each other in addition to the problem that the heat roller 276 is damaged. There is also the problem of being very difficult to remove from the system. Therefore, when the pressure of the print medium reaches an appropriate level, it is an important problem to properly set the locking force (locking force) of the coupling portion to release the openable coupling of the cover portion.

The present invention is to improve the problems as described above, by having a second top cover opening and closing structure that is not heat deformation or wear, it is possible to maintain a constant locking force (regardless of the period of use), The present invention provides an image forming apparatus that can easily adjust a locking force by changing a spring portion accordingly.

Hereinafter, a process in which the second upper cover part opening / closing structure 215 is operated will be described in detail by causing a jam phenomenon in the print medium P and increasing the pressure of the print medium P. FIG.

When a print medium is caught in the space between the fixing unit 275 and the rollers 278, one end of the second lower cover part 208 is opened upward as shown in FIG. 5B. Let's look at this process in more detail.

When the jamming of the print medium is intensified, the pressure pushing the print medium P upward on the second lower cover part 208 rises above a predetermined reference value to open the second lower cover part 208. Here, the pressure which is a predetermined reference value is preferably a pressure such that the guide claw 209 presses the heat roller 276 and does not damage the heat roller 276 such as scratching.

When the second lower cover part 208 is opened, as shown in FIG. 5B, a portion of the second lower cover part 208 contacts the second upper cover part 206 so as to contact the second upper cover part 206. Will be pushed upwards. This process will be described in more detail with reference to FIG. 6.

When the second lower cover portion 208 pushes up the second upper cover portion 206, the second upper cover portion 206 also moves to the cam portion 215a installed in the second upper cover portion 206. Will move in the same direction. That is, in FIG. 5B, the cam part 215a is rotated counterclockwise with respect to the bushing part 215b. Thereafter, the cam protrusion 215a 'presses the locking projection B of the bushing portion 215b and pushes it downward. Next, the bushing portion 215b vertically moves downward along the guide rib 215c 'of the bushing portion guide 215c while the spring portion 215d is contracted. By doing in this way, the 2nd upper cover part 206 starts to open by the printing medium P and the 2nd lower cover part 208 sequentially.

When the second upper cover portion 206 is further opened, as shown in FIG. 5C, the cam protrusion 215a ′ slides on the engaging jaw B of the bushing portion 215b from a moment and is shown in FIG. 6. Into the first groove (A) of the bushing portion 215b, and pushes the bottom surface of the first groove (A) in the first groove (A). This state continues until the second upper cover portion 206 is completely opened. At this time, a switch unit (not shown) is installed at a predetermined position of the main body 201 and is connected to the second upper cover part opening / closing structure 215 to operate so that the printing operation is stopped.

Next, an operation when the second upper cover portion 206 is closed will be described. When the print medium P having the jammed phenomenon is removed, the second lower cover part 208 and the second upper cover part 206 are sequentially closed. This process will be described in more detail with reference to FIGS. 5C and 6.

When the second lower cover part 208 is closed, the force pushing up the second upper cover part 206 by the second lower cover part 208 is removed. Therefore, the second upper cover portion 206 is closed by its own load. At this time, the cam portion 215a coupled to the second upper cover portion 206 also moves in the same direction as the second upper cover portion 206 moves. That is, in this embodiment, the cam portion 215a rotates clockwise with respect to the bushing portion 215b, and loses the force for pushing the bottom surface of the first groove A formed in the bushing portion 215b. Done. Therefore, the spring portion 215d is restored by the elastic force, and as the spring portion 215d is restored, the bushing portion 215b inserted thereto is also vertically moved upward. At this time, the cam protrusion 215a 'is placed on the locking projection B of the bushing portion 215b, as shown in FIG. 5A, out of the first groove A of the bushing portion 215b.

Meanwhile, as illustrated in FIG. 7, the bushing part 215b is guided by the guide ribs 215c 'of the bushing part guide 215c to smoothly move vertically. It is preferable that a constant gap d is formed between the second grooves C of 215b.

According to the present invention, there can be provided an image forming apparatus having an opening and closing structure of an upper cover portion capable of maintaining a constant locking force regardless of the period of use.

In addition, according to the present invention, there can be provided an image forming apparatus having an opening and closing structure of the top cover portion that can be easily adjusted to the locking force (locking force) according to the purpose of use.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art to which the art belongs can make various modifications and other equivalent embodiments therefrom. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the claims below.

Claims (5)

An image forming apparatus having an image formed on a printing medium, the image forming apparatus comprising a main body and an upper cover part rotatably installed on the main body, A cam portion installed around the rotational shaft of the upper cover portion, the cam portion having a cam protrusion; A bushing part in which the cam part is seated and vertically moves up and down according to the rotation of the cam part; And And an upper cover part opening / closing structure installed on the main body, the top cover part opening and closing structure including a spring part contracted or elastically restored according to the vertical movement of the bushing part and closely contacting the bushing part to the cam part. The method of claim 1, The upper cover part opening and closing structure, And a bushing part guide installed in the main body and guiding vertical movement of the bushing part and having a guide rib formed therein. The method of claim 1, And a second groove for accommodating the guide rib of the bushing part guide and a first groove for accommodating the cam protrusion, a latching jaw pressed by the cam protrusion, and a guide rib of the bushing part guide. The method of claim 1, The lower cover part is formed to be in contact with the print medium when the print medium is jammed on the transport path, and to open upward when the pressure of the print medium according to the jammed print medium rises above a predetermined reference value. And the upper cover portion is formed to open by contacting the lower cover portion when the lower cover portion is opened. The method according to any one of claims 1 to 4, And the upper cover part includes a first upper cover part and a second upper cover part, wherein the first upper cover part is fixed to the main body, and is configured to open and close only the second upper cover part.

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