JP2003192205A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase productivity in image forming and restrict bending propensity to paper and occurrence of a jam. <P>SOLUTION: This device comprises a reversing passage 24 for feeding paper S guided by a feed passage 23, a paper carrying passage 25 arranged on an extending surface of the reversing passage 24 in the reverse direction to the direction for feeding paper into the reversing passage 24, and a paper reversing means 20 that can switch between a feeding state where the paper S fed into the reversing passage 24 from the tip is switched back in a direction making the rear end as the tip for feeding into the paper carrying passage 25 and an open state where at least a part of the preceding paper S fed from the reversing passage 24 and the following paper S fed into the reversing passage 24 is allowed to overlap. Thereby, productivity in image forming can be increased by narrowing a paper feed interval, and bending propensity to the paper S and occurrence of the jam can be restricted since the paper S can be fed straight from the reversing passage 24 toward an image forming section 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention sends a sheet from the front end to a reversing path provided in a conveying path for conveying the paper to an image forming unit, and temporarily stores the paper. The present invention relates to an image forming apparatus having a function of performing switchback so that the sheet is conveyed to an image forming unit.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, sheets of sheets stacked and held in a sheet storage section are fed one by one and aligned by a registration roller that stops the leading edge position, and are registered in synchronization with the operation of the image forming section. By driving the roller,
Paper is being fed to the image forming unit in good timing. In this case, if the next sheet is fed from the sheet storage section while the leading edge of the sheet is stopped by the registration rollers, the preceding sheet and the succeeding sheet may overlap. Need to feed. In addition, the margin between the front and back paper must be taken into consideration because of the slip between the paper feed roller and the paper, the change in the paper transport speed with time and the environment, and the variation in the stop time for registration. It is difficult to improve productivity.

From this, for example, Japanese Patent Laid-Open No. 2001-130
As disclosed in 812 and the like, there is an image forming apparatus that improves the workability of image formation by narrowing the interval between the sheets fed to the image forming unit when image formation is continuously performed. Proposed. The outline thereof is shown below in FIG. FIG. 5 is a vertical sectional front view showing the schematic structure of the inside of an image forming apparatus using a conventional electrophotographic printer as an example.

An image forming apparatus A shown in FIG. 5 includes an image forming section 2 for forming an image on a sheet S fed from a sheet feeding tray 1, a fixing section 3, a sheet feeding passage 4, and a sheet feeding passage 4. It has a sheet conveyance path 6 and the like provided between it and the sheet discharge stacker 5.

The image forming section 2 includes a photosensitive member 7 which is rotationally driven.
A charger 8 for uniformly charging the surface of the photoconductor 7, a digital writing device 9 for writing an electrostatic latent image on the photoconductor 7, and toner attached to the electrostatic latent image on the photoconductor 7. By developing the toner image, a transfer belt 11 that transfers the developed toner image onto the sheet S, and a cleaning device 12 that removes residual toner on the photoconductor 7.
With.

A reversing path 14 is provided from the middle of the paper feed path 4 for guiding the paper S fed from the paper feed tray 1 to the image forming section 2 by the paper feed means 13 for separating and feeding the paper S one by one. A branch is provided, and a branch claw 15 is provided at a branch point of the inversion path 14. The upstream side 4 of the branch pawl 15 in the sheet feeding path 4
A conveyance roller 16 that conveys the sheet S is provided in the portion a, and an entrance roller 17 that sends the sheet S to the reversing path 14 is provided near the branching claw 15. In the portion of the paper feed passage 4 on the downstream side 4b of the branch claw 15, the reversing passage 14 is provided.
A conveyance roller 18 that conveys the sheet S fed to the image forming unit 2 and a registration roller 19 are provided.

The branch claw 15 has a triangular shape which becomes narrower toward the inner side of the reversing path 14, and when the sheet S is guided to the reversing path 14, it is driven clockwise to feed the sheet S from the reversing path 14. When it is sent to the passage 4, it is configured to be driven counterclockwise.

Sheet reversing means 20 is provided in the reversing path 14. The sheet reversing means 20 has a half-moon-shaped reversing roller 21 having a part of the outer periphery cut off and a driven roller 22 facing the reversing roller 21, and the sheet S fed from the leading end to the reversing path 14 is trailing end. Of the preceding sheet S sent from the reversing path 14 and the succeeding sheet S sent to the reversing path 14 by switching back so that the leading edge of the reversing path is sent to the sheet feeding path 4 from the reversing path 14. It can be switched to an open state that allows a part of them to overlap. Reversing roller 2 that rotates in the delivery state
1 is obtained during the period in which the sheet S is sandwiched between the outer peripheral surface of the driven roller 22 and the outer peripheral surface of the driven roller 22, and the open state is obtained during the period in which the reversing roller 21 is not in contact with the sheet S because the chipped portion is downward. .

According to such a configuration, the paper S being fed from the paper feed tray 1 is sent from the paper feed passage 4 to the reversing passage 14 to stand by, and the preceding paper S is fed to the image forming section 2. At this time, the sheet S is reversed from the reversing path 14 at the standby position so as to be switched back by the reversing roller 21 and the driven roller 22 and sent out to the sheet conveying path 6, thereby narrowing the interval between the sheets S and reducing the image. The forming productivity can be increased.

[0010]

The image forming apparatus A shown in FIG. 5 can obtain the effect that the interval between the sheets S can be narrowed to improve the productivity of image formation. However, the paper feed path 4 is from the paper feed tray 1 to the reverse path 14
The upstream side 4a up to the branch point and the downstream side 4b up to the image forming unit 2 from the branch point of the reversing path 14 are separately arranged in the vertical direction, so that the curved portion increases in the vertical direction. Considering the case of using thick cardboard having a strong rigidity, the bending radius of each of the upstream side 4a and the downstream side 4b of the sheet feeding passage 4 cannot be reduced, so that the overall height cannot be reduced.

When priority is given to reduction in overall height, the paper feed passage 4
The bending radius must be reduced, the use of thick paper is limited, and even if a paper S other than thick paper is used, a jam easily occurs.

Therefore, an object of the present invention is to satisfy the requirement of narrowing the interval between the fed sheets to enhance the productivity of image formation, and at the same time, to widen the types of usable sheets and prevent the occurrence of jams. That is.

It is a further object of the present invention to reduce the overall height dimension.

It is a further object of the present invention to reduce the total height dimension on condition that a plurality of paper feed trays are provided.

[0015]

According to another aspect of the present invention, there is provided an image forming apparatus, wherein a sheet feeding path for guiding a sheet fed by a sheet feeding means, and a sheet guided by the sheet feeding path are fed from the front end thereof. A reversing path for temporary storage, a paper conveying path arranged on an extension surface of the reversing path in a direction opposite to the feeding direction of the paper to the reversing path, and a paper sheet arranged on the paper conveying path. An image forming unit that forms an image on the sheet, a feed state in which the sheet fed from the leading end to the reversing path is switched back in a direction in which the trailing edge is the leading end, and is fed to the sheet conveying path; And a sheet reversing unit that is switchable to an open state in which at least a part of the preceding sheet and the succeeding sheet fed to the reversing path are allowed to overlap with each other.

Therefore, it is possible to send the paper sent to the reversing path substantially straight toward the paper carrying path in which the image forming section is arranged, without curving the paper.

According to a second aspect of the invention, in the first aspect of the invention, the paper transport path is provided substantially horizontally.

Therefore, it is possible to send out the paper sent to the reversing path to the paper carrying path in which the image forming section is arranged without curving, and it is possible to keep the overall height of the image forming apparatus low.

According to a third aspect of the present invention, in the second aspect of the present invention, one end is branched from the downstream side of the image forming section in the sheet conveying path and the other end is re-fed into the sheet feeding path. Provide a path.

Therefore, it becomes possible to supply the sheet on which the image is formed in the image forming section to the image forming section again through the sheet re-feeding path, the sheet feeding path and the reversing path.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the re-feeding path is curved with a bending radius equal to or greater than the bending radius of the sheet feeding path.

Therefore, when the paper on which the image has been formed is re-fed to the image forming section again, the paper can be reliably conveyed.

According to a fifth aspect of the present invention, in the second aspect of the present invention, a plurality of paper feed trays, one end of which is connected to the paper feed path, are provided below the reversing path and below the paper conveying path. It is arranged in different positions in the horizontal direction.

Therefore, it becomes possible to efficiently arrange more paper feed trays while saving space.

According to a sixth aspect of the present invention, in the first aspect of the invention, a manual feed passage for manually feeding the paper is connected to an end of the reversing passage on the side opposite to the paper conveying passage. It is provided.

Therefore, it is possible to feed the sheet from the manual feed path to the image forming section without curving the sheet.

According to a seventh aspect of the present invention, in the sixth aspect of the invention, a stopper that regulates an edge position of a sheet on the sheet conveying path side is provided in the reversing path so as to be retractable with respect to the reversing path. Has been.

Therefore, by advancing the stopper to the reversing path, the edge position in the insertion direction is regulated regardless of the size difference of the paper, and by retracting the stopper from the reversing path, the edge position is regulated. It is possible to send the sheet from the reverse path to the image forming unit.

The invention as defined in claim 8 is defined by claim 1 through claim 7.
In the invention described in any one of 1. above, the image forming system of the image forming unit is an electrophotographic system.

Therefore, it is possible to provide an electrophotographic image forming apparatus capable of sending out the paper sent to the reversing path to the paper carrying path in which the image forming section is arranged without curving.

Item 9 In the invention according to Item 8, the image forming unit comprises a digital writing device for writing digital data on the photoconductor.

Therefore, it is possible to send out the paper sent to the reversing path to the paper carrying path in which the image forming section is arranged without curving, and to provide an electrophotographic image forming apparatus for writing digital data on the photoconductor. Can be provided.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
Or, it demonstrates based on FIG. FIG. 1 is a vertical sectional front view showing a schematic internal structure of an image forming apparatus such as an electrophotographic printer, and FIGS. 2 and 3 are vertical sectional front views showing main parts of the image forming apparatus. The same parts as those described with reference to FIG. 5 will be described using the same reference numerals.

The image forming apparatus B in this embodiment is
It has a plurality of paper feed trays 1. These paper feed trays 1
In order to distinguish between the two, a, b, and c are added after the code 1. Further, the image forming apparatus B uses the selected paper feed tray 1
The image forming unit 2 that forms an image on the paper S fed from the fixing unit 3, the paper feed passage 23 that guides the paper S fed from each paper feed tray 1, and the paper feed passage 23. The sheet S has a reversing path 24 for feeding the sheet S from its front end and temporarily storing it, and a sheet conveying path 25 arranged on an extension surface of the reversing path 24 in the right direction. Inversion path 24
A manual feed path 26 is connected to the left side of the
A paper discharge roller 27 and a paper discharge stacker 5 are sequentially provided at the downstream end of the paper.

The image forming section 2 is provided on the sheet conveying path 25, and the configuration is the same as that described in FIG. 5, and the photoconductor 7, the charger 8 and the photoconductor 7 are statically stored as digital data. A digital writing device 9 for writing an electrostatic latent image, a developing device 10, a transfer belt 11, and a cleaning device 12
With.

The paper feed means 13 is provided for each paper feed tray 1. The manual feed path 26 is inclined slightly downward to the right with respect to the horizontal plane, but the reversing path 24 and the sheet conveying path 25 are arranged in the horizontal plane. A branch claw 15 and a turn roller 28 for feeding the paper S to the reversing path 24 are provided above the paper feeding path 23. The branch claw 15 has a triangular shape that narrows toward the inner side of the reversing path 24, and is driven clockwise when the paper S is guided to the reversing path 14,
When the sheet S is sent out from the reversing path 24 to the sheet conveying path 25, it is configured to be driven counterclockwise.

The sheet reversing means 20 is provided in the reversing path 24. The sheet reversing means 20 has a half-moon-shaped reversing roller 21 with a part of the outer periphery cut off and a driven roller 22 facing the reversing roller 21, and the sheet S fed from the leading end to the reversing path 24 is trailing end. Are fed back from the reversing path 24 to the sheet conveying path 25, and the preceding sheet S sent from the reversing path 24 and the subsequent sheet S sent to the reversing path 24
It is possible to switch to an open state in which at least a part of the above is overlapped, and the configuration is exactly the same as that described in FIG. Further, the reverse path 24 is provided with a jogger 29 that regulates the position of the paper S in the width direction even if the paper S has different width sizes.

Further, in the paper transport path 25, the fixing unit 3
A sheet re-feeding path 30 is provided, one end of which branches from the sheet feeding roller 27 and the other end merges with the sheet feeding path 23.
In addition, at the branch point between the paper transport path 25 and the re-feed path 30,
A branching claw (not shown) is provided to selectively switch the conveyance path of the sheet S on which the image is formed by the image forming unit 2 to the direction of the sheet discharge stacker 5 or the sheet refeed path 30. Further, the re-feeding path 30 has a plurality of pairs of conveyance rollers 3 for conveying the paper S
1 is arranged. The paper feed trays 1a and 1b are vertically arranged below the horizontal reversing path 24, and the other paper feed tray 1c is below the paper transport path 25 and below the refeed path 30. It is located in. The paper feed path 23 changes the direction of the paper S sent out horizontally from each paper feed tray 1 in the vertical direction, and further connects the upper part and the paper feed tray 1 to guide it toward the horizontal reversing path 24. Is bent. The sheet re-feeding path 30 also feeds the sheet S to the sheet feeding path 2
It is bent in a loop shape to guide 3. The bending radius of the sheet re-feeding path 30 is set to a value equal to or larger than the bending radius of the sheet feeding path 23.

In such a structure, as shown in FIGS. 1 and 2, the state in which the reversing roller 21 is stopped with the chipped portion facing downward is the state in which the sheet S is open.
Therefore, the paper S in the desired desired paper feed tray 1 is selected.
Can be separated and fed by the sheet feeding means 13 and fed to the reversing path 24. At this time, the branch claw 15 is displaced clockwise and the jogger 29 is opened slightly wider than the width of the sheet S. When the reversing roller 21 is driven in the counterclockwise direction, the sheet S is nipped by the driven roller 22 and the outer peripheral surface of the reversing roller 21 other than the chipped portion, so that the sheet conveying path 2
It is sent out toward 5. In the process of being sent out, the paper S is delivered to the transfer belt 11, and in the open state in which the reversing roller 21 is stopped with the chipped portion facing downward,
It is allowed to feed the succeeding paper S fed from the paper feed tray 1 into the reversing path 24. At this time, at least a part of the preceding sheet S sent out from the inversion path 24 and the subsequent sheet S sent to the inversion path 24 overlap each other. Therefore, it is possible to feed the sheet S to the image forming unit 2 with the gap between the preceding sheet S and the succeeding sheet S narrowed, thereby improving the productivity of image formation.

As described above, in the initial stage of feeding the sheet S of the reversing path 24 to the sheet transporting path 25, the branch claw 15 is turned counterclockwise to narrow the jogger 29 and regulate the width position of the sheet S. In this case, it is preferable in terms of skew correction that the width of the jogger 29 is narrower than the actual width of the sheet S by about 1 mm to bend the sheet S. Paper S in the reverse path 24
When the paper is started to be sent to the paper transport path 25, the branch claw 15 is turned counterclockwise and the jogger 29 is opened to prepare for the subsequent paper S feed.

In the paper feeding, in addition to the paper feeding from the paper feeding tray 1, the paper S is inserted into the reversing path 24 from the manual feeding path 26, and the reversing roller 21 and the driven roller 2 are inserted from the reversing path 24.
With 2, it is possible to select a usage mode in which the paper S is fed to the image forming unit 2. In this case, the sheet S can be fed without curving in the process from the manual feed passage 26 to the image forming section 2, and thus even when thick paper is used, the sheet S has a tendency to fold and a jam occurs. It is possible to avoid the above and feed in a stable state.

As shown in FIG. 3, the sheet conveying path 2 for the sheet S is shown.
A stopper 32 that regulates the edge position on the fifth side is provided so as to be retractable with respect to the reversing path 24, and when the paper is fed from the manual feeding path 26, the stopper 32 is advanced to the reversing path 24, so that the size of the paper S is different. Regardless of, the edge position in the insertion direction can be regulated. In this case, by retracting the stopper 32 from the reversing path 24, the sheet S whose edge position is regulated can be sent out from the reversing path 24 to the image forming unit 2.

When performing double-sided printing, the image forming section 2
The sheet S having the image formed on the upper surface thereof by the re-feeding path 30,
The sheet is re-fed to the sheet conveying path 25 via the sheet feeding path 23 and the reversing path 24, and the image forming unit 2 forms an image on the re-fed sheet S. The double-sided printed paper S is discharged onto the paper discharge stacker 5.

By the way, the paper transport path 25 is the reverse path 24.
Inversion path 2 in the direction opposite to the feeding direction of the paper S to the sheet
Since the sheets S are arranged on the extended surface of the sheet 4, the sheet S fed into the reversing path 24 can be delivered substantially straight to the sheet transporting path 25 in which the image forming unit 2 is arranged without being curved. In particular, since the reversing path 24 and the sheet conveying path 25 are horizontally arranged, even if the sheet feeding trays 1a and 1b are vertically stacked, the total height of the image forming apparatus B is greatly reduced. be able to. Further, the paper feed trays 1a and 1b are placed below the reversing path 24,
By arranging the paper feed tray 1c below the paper transport path 25, it is possible to efficiently arrange more paper feed trays 1a, 1b, 1c while saving space.

Since the overall height can be kept low as described above, the bending radii of the sheet feeding path 23 and the sheet refeeding path 30 can be expected to be larger than in the conventional case, so that even when the thick sheet S is used. It is possible to prevent the sheet S from having a bending tendency and from causing a jam. Further, since the bending radius of the sheet re-feeding path 30 can be set to be equal to or larger than the bending radius of the sheet feeding path 23, a range in which a folding tendency does not occur in the sheet feeding process from the sheet feeding path 23 to the image forming unit 2. Even if the paper sheet S having the maximum thickness is used,
It is possible to avoid a tendency to break in the process of being transported 0. For example, even if double-sided printing is performed using 110K paper S, the paper S does not have a bending tendency.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a front view showing the external structure of a copying machine, a facsimile machine, or a multifunction machine.

FIG. 4 shows a state in which the image reading device C for reading an image is mounted on the upper part of the casing 33 of the image forming device B described in the above embodiment. Therefore, by mounting a control unit (not shown) that causes the image forming apparatus B to output the image data read by the image reading apparatus C, the sheet S sent to the reversing path 24 as described above.
It is possible to provide a copying machine that can send the sheet to the sheet conveying path 25 in which the image forming unit 2 is arranged without curving, and can keep the total height dimension low.

In addition to the configuration shown in FIG. 4, a modem (not shown) connected to an external telephone line, and a reception data memory (not shown) for renewably storing received data received through the modem are provided. The image forming apparatus B is provided with the received data.
The control unit (not shown) for switching the control for outputting the image data and the control for transmitting the image data read by the image reading device C through the modem is mounted, so that the sheet S sent to the reversing path 24 can be controlled. It is possible to provide a facsimile machine which can be sent out to the sheet conveyance path 25 in which the image forming unit 2 is arranged without being bent, and whose overall height dimension can be kept low.

Further, in addition to the configuration of FIG. 4, a modem (not shown) connected to an external telephone line, and a reception data memory (not shown) for renewably storing reception data received through the modem are provided. Provided, control for outputting received data from the image forming apparatus B, control for transmitting image data read by the image reading apparatus C through a modem, control for outputting image data read by the image reading apparatus C from the image forming apparatus B. By mounting a control means (not shown) for selectively executing the above, it is possible to send out the paper S sent to the reversing path 24 to the paper carrying path 25 in which the image forming unit 2 is arranged without curving. In addition, a multifunction machine that can keep the overall height low, for example, a copying function,
It is possible to provide a multi-function peripheral having a facsimile function.

[0050]

According to the first aspect of the present invention, it is possible to reduce the interval between the sheets to be fed to enhance the productivity of image formation, and further, the sheet conveying paths are arranged on the extension surface of the reversing path. Therefore, the sheet sent to the reversing path can be sent out to the sheet transporting path in which the image forming unit is arranged without curving. Along with this, it is possible to prevent the paper from being bent and jamming.

According to the invention described in claim 2, in the invention described in claim 1, since the sheet conveying path is provided substantially horizontally, in addition to obtaining the same effect as the case described in claim 1. Therefore, the overall height of the image forming apparatus can be kept low.

According to a third aspect of the present invention, in the second aspect of the present invention, one end is branched from the downstream side of the image forming portion in the sheet conveying path and the other end is joined to the sheet feeding path. In addition to obtaining the same effect as in the case of claim 2, the sheet on which the image is formed in the image forming unit is re-imaged through the re-feeding path, the paper feeding path and the reversing path. Can be supplied to the unit for double-sided printing.

According to the invention described in claim 4, in the invention described in claim 3, since the re-feeding path is curved with a bending radius equal to or larger than the bending radius of the feeding path, In addition to obtaining the same effect as, it is possible to reliably convey the paper after the image formation when the paper is re-fed to the image forming unit.

According to the fifth aspect of the present invention, in the second aspect of the present invention, the plurality of paper feed trays whose one end is connected to the paper feed path are horizontal below the reversing path and below the paper conveying path. Since they are arranged at different positions in different directions, in addition to obtaining the same effect as in the case of claim 2, it is also possible to arrange more paper feed trays efficiently while saving space. You can

According to the sixth aspect of the present invention, in the first aspect of the invention, since the manual feed passage for manually feeding the paper is provided by being connected to the end of the reversing passage, the manual feed passage is provided. The paper can be fed without curving in the paper feeding process from the printer to the image forming unit, which allows the paper to be securely fed even when thick paper is used without causing a crease and jamming. can do.

According to the invention described in claim 7, in the invention described in claim 6, a stopper for restricting an edge position of the sheet on the sheet conveying path side is provided in the reversing path so as to be retractable with respect to the reversing path. Therefore, in addition to obtaining the same effect as in the case of claim 6, by advancing the stopper to the reversing path, the edge position in the insertion direction is regulated regardless of the difference in the size of the paper, and the stopper is By retreating from the reversing path, it is possible to send out the paper whose edge position is regulated to the image forming unit from the reversing path.

According to the invention described in claim 8, in the invention described in any one of claims 1 to 7, since the image forming system of the image forming section is an electrophotographic system, the sheet fed into the reversing path is curved. It is possible to provide an electrophotographic image forming apparatus that can send the image to the sheet conveying path in which the image forming unit is arranged without performing the operation.

According to the above invention, in the invention according to claim 8, since the image forming section is provided with a digital writing device for writing digital data on the photoconductor, the paper fed into the reversing path is curved. It is possible to provide an electrophotographic image forming apparatus that can send the image data to the sheet conveyance path in which the image forming unit is arranged without writing and write the digital data on the photoconductor.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional front view showing the schematic structure of the inside of an image forming apparatus using an electrophotographic printer as an example according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view showing a main part of the image forming apparatus.

FIG. 3 is a vertical sectional front view showing a main part of the image forming apparatus.

FIG. 4 is a front view showing a copying machine, a facsimile machine, or a multifunction machine according to a second embodiment of the present invention.

FIG. 5 is a vertical cross-sectional front view showing a schematic internal structure of an image forming apparatus using a conventional electrophotographic printer as an example.

[Explanation of symbols]

1,1a-1c Paper feed tray 2 Image forming section 7 photoconductor 9 Digital writing device 13 Paper feeding means 20 Paper reversing means 23 Paper feed path 24 Inversion road 25 Paper transport path 26 Bypass passage 30 Refeed path 32 stopper

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3F053 BA03 BA14 BA25 BA27 EB01                       EB04 LA01 LB03                 3F063 AA01 BA10                 3F100 AA02 CA15 EA03                 3F102 AA01 AB01 BA02 BB02 BB04                       EA14 FA03 FA07 FA08

Claims (9)

[Claims] 1. A paper feed passage for guiding the paper fed by the paper feed means, a reversing passage for feeding the paper guided by the paper feeding passage from the leading end thereof and temporarily storing the paper, and the reversing passage. A sheet conveying path arranged on an extension surface of the reversing path in a direction opposite to the sheet feeding direction to the sheet, an image forming unit arranged on the sheet conveying path to form an image on the sheet, and the reversing path. A feeding state in which the sheet fed from the leading end is switched back in a direction in which the trailing end is the leading end and is fed to the sheet conveying path, a preceding sheet fed from the reversing path and a subsequent sheet fed to the reversing path. An image forming apparatus including: a sheet reversing unit that is switchable to an open state that allows at least a part of the above. 2. The image forming apparatus according to claim 1, wherein the paper transport path is provided substantially horizontally. 3. The image forming apparatus according to claim 2, further comprising a re-feeding path having one end branched from a downstream side of the image forming unit in the paper conveyance path and the other end joined to the paper feed path. 4. The re-feeding path is curved with a bending radius equal to or greater than the bending radius of the paper feeding path.
The image forming apparatus described. 5. A plurality of paper feed trays, one end of which is connected to the paper feed path, are arranged at different positions in the horizontal direction below the reversing path and below the paper transport path. 2. The image forming apparatus according to 2. 6. The image forming apparatus according to claim 1, wherein a manual feeding passage for manually feeding the paper is provided so as to be connected to an end of the reversing passage on the side opposite to the paper transporting passage. 7. The image forming apparatus according to claim 6, wherein the reversing path is provided with a stopper that restricts an edge position of a sheet on the sheet conveying path side so as to be retractable with respect to the reversing path. 8. The image forming apparatus according to claim 1, wherein the image forming system of the image forming unit is an electrophotographic system. 9. The image forming apparatus according to claim 8, wherein the image forming unit includes a digital writing device that writes digital data on a photoconductor.