JPH1081449A - Document supply device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a device of a simple mechanism, and efficiently process a double-sided document in a small type by providing a first carrying direction switching means and a second carrying direction switching means. SOLUTION: A first carrying direction switching means 8 is arranged in a connecting part of a first carrying passage a1 of a circulative path and a switchback path (d), and the carrying direction of a document G is switched to the switchback path (d) or the circulative path (a). A second carrying direction switching means 9 is arranged in a connecting part of a second carrying passage a2 of the circulative path (a) and a discharge path (c), and the carrying direction of the document G is switched to the discharge path (c) or the circulative path (a). When the first carrying direction switching means 8 exists in a switching position shown by a continuous line, it is carried in the direction of the first carrying passage a1 of the circulative path (a), and when the means exists in a position shown by a two-dot chain line, the document G carried by the first carrying passage a1 of the circulative path (a) is guided in the direction of a reversibly rotating roller 10 arranged in the switchback path (d) to be switched back in a space 24 added to the switchback path (d).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document supply apparatus for automatically supplying a document to a document reading section of an image forming apparatus such as an electrophotographic copying machine. The present invention relates to an image forming apparatus using the document supply device.

[0002]

2. Description of the Related Art As is well known, in an image forming apparatus such as an electrophotographic copying machine, a document is automatically supplied to a document reading section. In recent years, a document feeder capable of processing a double-sided document having images on both sides has been desired.

For this reason, a document feeder capable of processing a double-sided document having images on both sides has been proposed. For example, there is a document processing machine disclosed in Japanese Patent Application Laid-Open No. 7-175279. This document processor has two modes,
In the first mode, a single-sided document is read and completely discharged directly to the paper discharge tray. In the second mode, the first side of the double-sided document is read and fed once to the paper discharge tray. The sheet is switched back without being completely discharged onto the tray, and is again fed to the document feeding path via the double-sided feeding path. Then, after reading the second side and feeding it to the paper output tray,
Even if two-sided originals are sequentially stacked on the output tray, the originals are stacked with the first side down so that the page order is aligned. The sheet is again fed to the document feeding path via the path, and then discharged to the sheet discharge tray and stacked. Therefore, a double-sided document is circulated by a roller for discharging and reversing the entrance of the sheet discharge tray and a double-sided feeding path for feeding the document from the sheet discharging tray to the document feeding path. The discharge of the double-sided document is reversed by the roller, and is discharged to the discharge tray by the roller via the same path as the document to be read on the second side.

Further, for example, there is a sheet conveying apparatus disclosed in Japanese Patent Application Laid-Open No. 8-133551 (Japanese Patent Application No. 6-298816). This technique reads the second side to discharge the two-sided originals so that the pages are stacked with the first side down so that the page order is aligned even when the two-sided originals are sequentially stacked on the paper output tray. Reversing at another reversing section, which is later provided at a different location not on the output tray (switchback)
At the very least, the paper is discharged to the paper discharge tray. That is, the second
This is a technique similar to that of Japanese Patent Application Laid-Open No. 7-175279 in that the reversal of a double-sided document for reading a surface is performed on a discharge tray.

[0005]

However, in reading a double-sided document according to the technique disclosed in Japanese Patent Application Laid-Open No. HEI 7-175279, if the documents are sequentially stacked on the discharge tray so that the pages are arranged in order, the document is not read. 3 reading units
You need to pass twice. During the third passage of the original, the original is passed through the original reading section even though the original is not read, thereby causing contamination of the original reading section and causing a defective read image. Or the document reading section needs to be cleaned frequently. The original reading unit is ready to read the next original after reading of the original is completed.However, in order to discharge the originals in order, the original reading unit does not read the original. , It is not possible to feed the next document even after the reading is completed, which is an adverse effect of improving the reading speed of the document. Further, there is a drawback that the distance for transporting the document is increased, and the time for transporting the document is correspondingly increased, so that the productivity of image formation is reduced, and the damage to the document due to pressure and friction applied during transport is increased. . In addition, since the document is reversed on the output tray, the user mistakenly picks up the document that is output on the output tray for reversing as the document that has been ejected after the process is completed, and removes the inverted document. Sometimes. In this case, the document processing machine stops due to paper conveyance failure. In addition, even in the image forming apparatus main body where a double-sided image is being formed, it must be stopped even during image formation, which causes a problem of stopping the entire apparatus.

Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 8-133551, similar to the above-mentioned Japanese Patent Application Laid-Open No. 7-175279, since a two-sided original is reversed on a discharge tray, a paper transport of a similar original processing machine is performed. This causes a problem of stopping due to a defect and stopping the entire image forming apparatus. Further, a plurality of reversing processing units are required, and the provision of such a reversing processing unit requires a drive transmission mechanism for the plurality of reversing rollers and a control mechanism therefor. A complicated control mechanism is required.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the conventional document feeder that handles a two-sided document,
An object of the present invention is to provide a document feeder of an image forming apparatus which is small in size, has a simple mechanism, and is capable of efficiently processing a double-sided document with high productivity.

[0008]

That is, in order to solve the above-mentioned problems, the features of the document supply apparatus according to the first aspect are as follows.
In a document feeder of an image forming apparatus including a paper feed stacker for loading a two-sided document, a discharge stacker for loading a two-sided document after reading, and a circulation path having a document reading position, A supply path for supplying a two-sided document to the circulation path, a discharge path for discharging the two-sided document after reading to the discharge stacker, and a two-sided document arranged below the supply path or the sheet supply stacker. A switchback path for switching back and turning over, and a first transport direction switch provided at a connection portion between the circulation path and the switchback path, for switching a transport direction of the document to the circulation path or the switchback path. Means, provided at a connection portion between the circulation path and the discharge path, and a conveying direction of the document to the circulation path or the discharge path. In further comprising a second conveying direction switching means for changing Ri.

The document feeder according to the present invention is characterized in that when only one side of the document is read, the first transport direction switching means guides the document to the circulation path, and the second transport direction switching means. Guides the document to the discharge path, and when reading both sides of the document, the first transport direction switching means guides the document to the switchback path, and the second transport direction switching means controls the document after the one-side reading is completed. Is to guide the document to the circulation path and to guide the document after the both-side reading is completed to the discharge path.

The document feeder according to claim 3 is characterized in that the circulating path includes a first conveying path extending from a connection portion with the supply path to a connection portion with the discharge path, and the discharge path. And a second transport path from a connection portion to a connection portion with the supply path.

The document feeder according to a fourth aspect is characterized in that the paper feed stacker, the paper discharge stacker, and the switchback path are arranged on the same side with respect to the reading position.

A feature of the document supply apparatus according to the fifth aspect is that the paper feed stacker, the paper discharge stacker, and the switchback path are arranged in a stack from the top.

A feature of the document supply apparatus according to the present invention is that the switchback path is provided in a space below the discharge stacker.

According to a seventh aspect of the present invention, the switchback path is provided with a reversible reversing roller capable of normal and reverse rotation, and the document is switched back by switching the rotation direction of the reversible roller. It is in.

A feature of the document supply device according to the present invention is that the reversible roller is configured such that a pair of rollers can be separated from each other, and is separated when the document extends over the circulation path and the switchback path. .

The document supply apparatus according to the ninth aspect is characterized in that the discharge path is provided with a discharge roller that can rotate in only one direction.

A feature of the document supply apparatus according to the tenth aspect is that the circulation path is formed along the outer peripheral surface of one feed roller.

The image forming apparatus according to the eleventh aspect is characterized in that a paper feed stacker for loading a document, a discharge stacker for loading a document after reading is completed, document reading means for reading a document image, and A circulation path for guiding a document via document reading means, a supply path for supplying a two-sided document from the paper feed stacker to the circulation path, and discharging the document after reading to the discharge stacker A discharge path, a switchback path disposed below the supply path or the paper feed stacker for switching back and reversing the original, and provided at a connection between the circulation path and the switchback path. A first transport direction switching means for switching a transport direction of a document to the circulation path or the switchback path, and a connection between the circulation path and the discharge path. Provided, lies in and a second conveying direction switching means for switching the conveying direction of the document to the circulation path or the discharge path.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. The illustrated embodiment is an example in which the present invention is applied to an electrophotographic copying machine which is one of image forming apparatuses. A platen glass, that is, a platen 2 is disposed on an upper part of a body 1 of the electrophotographic copying machine. On one side, a document reading section X using a CCD element (not shown) is provided.

An apparatus housing 3 of the original supply apparatus according to the present invention is located on the platen 2. The apparatus housing 3 is provided with a paper feed stacker 4 located above the platen 2, and A plurality of documents G can be stacked on the paper stacker 4 in a stacked state.

A circulation path a is formed on the outer peripheral surface 5a of the large-diameter feed roller 5 facing the document reading section X. The circulating path a has a double-sided connection between the first transport path a1 for transporting the document G from the connection part with the supply path b to the connection part with the discharge path c and the connection part between the discharge path c and the supply path b. And a second conveyance path a2 for circulating and conveying the original. When the original G is a single-sided original, the original G is supplied from the paper feed stacker 4 to the first transport path a1 of the circulation path via a supply path b that transports the original G one by one. The document G for which the image reading process has been completed by the document reading unit X provided along one transport path a1 is
The paper is discharged and stacked on a paper discharge stacker 7 located substantially below and directly below the paper feed stacker 4 through a discharge path c including a discharge roller 6.

When the original G is a double-sided original, the double-sided original G whose front side has been read is conveyed to a switchback path d provided below the discharge path c in the same manner as in the case of a single-sided original. After being switched back by the switchback path d, the sheet is again conveyed to the circulation path a, sent to the first conveyance path a1 via the second conveyance path a2, Is read.

In order to perform these image reading processes,
A first transport direction switching means 8 is disposed at a connection portion of the circulation path a between the first transport path a1 and the switchback path d, and switches a transport direction of the document G to the switchback path d or the circulation path a. Switch. A second conveyance direction switching means 9 is disposed at a connection portion of the circulation path a between the second conveyance path a2 and the discharge path c, and switches the conveyance direction of the document G to the discharge path c or the circulation path a. . That is, FIG.
As shown in the figure, when the first transport direction switching means 8 is at the switching position shown by the solid line, the first transport path a1 of the circulation path a
And the document G conveyed along the first conveyance path a1 of the circulation path a when it is at the position indicated by the two-dot chain line.
Is guided in the direction of the reversible roller 10 provided in the switchback path d in order to switch back in the space 24 provided in the switchback path d.

The second transport direction switching means 9 at the switching position shown by the solid line closes the entrance of the discharge path c, and transfers the original G transported from the switchback path d along the circulation path a to the circulation path a. a in the direction of the second transport path a2, and is guided so as to circulate in the second discharge transport path a2 along the outer peripheral surface 5a of the feed roller 5, and at the position indicated by the two-dot chain line. , The first transport path a1 of the circulation path a
A single-sided original G conveyed along the paper path, or a double-sided original G that has been read from the switchback path d and conveyed along the circulating path a, is directed in the direction of the discharge path c. Drain into 7.

Referring to FIG. 2, the supply path b and the first
The details of the mechanism of the circulation path a, the switchback path d, and the discharge path c including the transport path a1 and the second transport path a2 will be described. The kick roller 11, the supply roller 12, and the separation A feeding mechanism composed of a member 13 is arranged, and the originals G stacked in a stacked state on the paper feed stacker 4 in a state where the surface of the original G faces upward by operation of the feeding mechanism are arranged in order from the top one. The sheets are sent out one by one to the supply path b.

In the supply path b, a first registration roller 14 and a second registration roller 15 adjacent to each other in the feeding direction of the document G are arranged, and the first registration roller 14 and the second registration roller 15 The document G is sent toward the first transport path a1 of the circulation path a by the rotation. The supply roller 12 and the first registration roller 14 are rotationally driven in one direction only by a drive motor M1 via a one-way clutch OW that transmits only one-way rotational movement.

The feed roller 5 of the circulation path a is driven to rotate in the direction of the arrow, and two rolling rollers 16 and 17 are rolled on the outer peripheral surface 5a of the feed roller 5 so that the original G is The document G is fed toward the document reading section X in a state of being in close contact with the outer peripheral surface 5 a. In the document reading section X, the surface of the document G is brought into close contact with the surface of the platen 2 by the pressing member 18.

As shown in FIG. 3, a reversible reversing roller 10 which can be rotated forward and backward is disposed in the switchback path d. A driven roller 20 pressed by a pressure spring 19 is provided around the reversing roller 10. Is transferred. That is, the switchback path d is established by the rolling contact / separation of the driven roller 20 separated from the reversible roller 10 by the excitation of the electromagnetic solenoid SOL and the forward / reverse rotation of the reversible roller 10.
The conveyance timing of the two-sided original G conveyed to the original is controlled.

The reversible roller 10 is driven by a forward / reverse rotation motor M2 shown in FIG. 2. The forward / reverse rotation motor M2 controls a transmission timing of power and a one-way transmission of only one-way rotational movement.・
The feed roller 5 and the discharge roller 6 are also driven via the clutch OW.

The supply path b, the circulation path a including the first transport path a1 and the second transport path a2, the switchback path d, and the discharge path c include original detection sensors S1 to S6 shown in FIG. These document detection sensors S1 to
By S6, the leading edge and the trailing edge of the document G are detected.

The document G manually placed on the surface of the platen 2 is placed in close contact with the surface of the platen 2 by the pressure plate 25. In order to form the pressure plate 25, the housing G of the document supply device is used. An elastically deformable porous layer 22 is laminated on the lower surface of a support plate 21 made of a hard resin, which constitutes the bottom surface of 3, and the porous layer 22 is covered with a flexible surface layer 23. Therefore, the switchback path d
The leading end g1 of the double-sided original G conveyed inside is disposed on the same side of the circulation path a below the paper supply stacker 4 and the paper supply path b, and more specifically, is supported by the paper discharge stacker 7. The document G is guided into the space 24 surrounded by the plate 21 and guided by the bottom surface 7a of the discharge stacker 7 having a small coefficient of friction and the upper surface 21a of the support plate 21, so that the original G is not bent. , Can switch back.

The document feeder of the image forming apparatus according to the illustrated embodiment has the above-described configuration.
4 is a single-sided document, the document G supplied from
In the state shown in FIG. 4A, the paper is discharged from the switchback path d through the discharge path c onto the paper discharge stacker 7, and when the document is a double-sided document, the paper is discharged in the state shown in FIG. This means that the sheet has been discharged to the stacker 7.

First, in the case of reading processing of a one-sided original,
The originals G stacked in a stacked state on the paper feed stacker 4 with the surfaces of the originals G facing up are in a state where the surfaces of the originals G face down while being transported by the first transport path a1 of the circulation path a. Therefore, the paper is discharged onto the paper discharge stacker 7 via the discharge path c directly from the first transport path a1. That is, in the case of the reading process of the document G having the page order having the image only on the front surface, the read document G is sequentially stacked on the discharge stacker 7 with the surface of the document G facing down. Even if these read originals G are taken out of the discharge stacker 7 as they are, there is no need to rearrange the page order of the originals G again.

When the original G to be read is a two-sided original, the two-sided original is stacked in a stacked state on the sheet feeder 4 with its front side facing upward like a one-sided original. Original G that has finished reading the front side
As shown in FIG. 4 (b), once is transferred from the tip g1 to the switchback path d, and the switchback path d
After a switchback pass in the space 24 attached to the second path, the sheet is circulated and conveyed from the rear end g2 through the second conveyance path a2 of the circulation path a, and the document reading section X performs a back surface reading process.

Thereafter, the double-sided document G is conveyed again from the rear end g2 to the switchback path d, and is switched back in the space 24 attached to the switchback path d, and then from the front end g1 to the first conveyance path a1. Conveyed, discharge path c
The paper is discharged through. Therefore, even in the case of a double-sided original, the original G for which the reading process has been completed is sequentially stacked on the discharge stacker 7 with the surface of the original G facing down. Even if a document is taken out of the discharge stacker 7 as it is, there is no need to rearrange the document page order again.

Next, the details of the double-sided document reading process will be described with reference to the time sequence shown in FIG. 5. When the double-sided processing mode is selected by the operator, the first transport direction switching means 8 moves to the position indicated by the two-dot chain line. Then, the second transport direction switching means 9 is switched to the position shown by the solid line.

Thereafter, the originals G placed on the paper feed stacker 4 are fed one by one to the paper feed path b by driving the kick roller 11 and the paper feed roller.
1, when the leading end g1 of the document G is detected,
The kick roller 11 and the paper feed roller stop rotating, and the first
When the registration roller 14 starts to rotate and the document G is
To the first transport path a1. Next, after a predetermined time elapses according to the setting of the timer, the feed roller 5, the reversible roller 10 and the paper discharge roller 6 start rotating, and the discharge of the original G remaining in the circulation path a, the switchback path d, and the discharge path c is prompted. However, when the leading edge g1 of the document G is detected by the document detection sensor S5, the rotation of the feed roller 5, the reversible roller 10 and the discharge roller 6 is temporarily stopped. Is read while being conveyed in the sub-scanning direction by the document reading section X.

When the reading process of the front side of the original G is completed and the trailing end g2 of the original G is detected by the original detection sensor S5, the feed roller 5, the reversible roller 10 and the discharge roller The paper roller 6 is stopped, and the trailing end g2 of the document G is detected by the document detection sensor S3. Next, based on the signal of the document detection sensor S3, the reverse rotation of the reversible roller 10 causes the second end of the circulation path a
The switch is switched back to the transport path a2. In this case, the trailing end g2 of the document G is guided by the outer peripheral surface 5a of the stopped feed roller 5 and the second transport direction switching means 9 and is transported to the second transport path a2 of the circulation path a. When the trailing end g2 of G is detected by the document detection sensor S6 before the second registration roller 15, the reversible roller 10 is stopped, and at the same time, the electromagnetic solenoid SOL is excited to cause the driven roller 20 to rotate. , The driving force of the reversible roller 10 on the document G is eliminated.

Next, although the feed roller 5 starts rotating by the detection of the document detection sensor S6, when the rear end g2 of the document G is detected by the document detection sensor S5, the signal of the document detection sensor S5 causes the feed to be performed. The rotation of the roller 5, the reversible roller 10 and the paper discharge roller 6 is temporarily stopped, and the first transport direction switching means 8 and the second transport direction switching means 9 are respectively switched to the positions indicated by the two-dot chain lines.

Subsequently, the feed roller 5 and the discharge roller 6 are driven, and at the same time, the reversible roller 10 is
, The forward rotation of the original G is started, and the original G with the back side downward is conveyed to the original reading unit X, and the back side is also read, and the rear end g2 of the original G is switched to the switchback path d. At the rear end g of the original G
3, the driven roller 20 is separated from the reversible roller 10 as shown in FIG.
Even if the first side remains in the switchback path d, the rear end g2 of the document G is taken in the switchback path d without any trouble.

The reading of the back side of the original G is completed.
When the leading edge g1 of the document G is detected by the document detection sensor S3, the reversible roller 10 rotates in the reverse direction and the second transport direction switching means 9 is switched to the position indicated by the two-dot chain line, and the leading edge g1 of the document G stops. Outer peripheral surface 5 of feed roller 5
The document G is guided by the first conveyance path a1, is directed to the discharge path c by the second conveyance direction switching means 9, is discharged onto the discharge stacker 7 by the rotation of the discharge roller 6, and the rear end g2 of the document G is The discharge roller 6 stops after a certain period of time from the signal detected by the detection sensor S4.

[0042]

As is apparent from the above description, according to the present invention, a document having undergone both-side reading is inverted downstream of the document reading section and upstream of the discharge path and discharged to the discharge tray. Therefore, it is not necessary to circulate the document even though the document is not read as in the related art, so that the transport distance can be shortened, and the next document can be immediately transported to the document reading unit and read. Can be shortened, and the productivity of image formation can be increased. Furthermore, since the document does not need to pass through the document reading unit three times, it is sufficient to perform the scanning twice, so that the damage to the document can be reduced, and the contamination of the document reading unit can be reduced. And not. In addition, since the original is reversed in a dedicated switchback path and space that is not on the output tray, and the original is not discharged onto the output tray for the inversion, the user is required to finish the process and discharge the original. There is no possibility of taking out the inverted document by mistake because it is a mistaken document, and there is no stop due to paper conveyance failure of the document feeder or stop in the middle of image formation in the image forming apparatus main body while forming a double-sided image. Does not cause the trouble of stopping.

If the paper feed stacker, the paper discharge stacker, and the switchback path are arranged on the same side with respect to the reading position, the projection area of the document feeder can be made relatively small, so that the apparatus can be downsized.

When the paper feed stacker, the paper discharge stacker, and the switchback path are arranged in order from the top, a document flowing from the paper supply stacker to the switchback path and a document flowing from the switchback path to the paper discharge stacker are arranged. Do not intersect with each other, so that the flow of the document is smooth and the productivity for the double-sided document is improved.

If the switchback path is provided in a space below the sheet discharge stacker, the space in the document supply device is effectively used, which leads to a reduction in size of the device.

Further, by providing a reversible roller capable of normal and reverse rotation in the switchback path, the document can be switched back stably and reliably.

Further, by making the reversible roller composed of a pair of rollers separable, the original is sent out from the switchback path to the circulation path for reading the back side of the original, and the trailing end of the original still passes through the pair of reversible rollers. Even if the tip reaches the position of the pair of reversing rollers, no jam occurs, so it is not necessary to make the circulation path longer than necessary, and high feeding reliability can be achieved with a small device. can get.

Further, it is sufficient that a discharge roller rotatable in only one direction is provided in the discharge path, whereby the mechanism and control of the apparatus are simplified.

Further, if a circulation path is formed along the outer peripheral surface of one feed roller, the leading and trailing edges of a double-sided document can be effectively guided on the same outer peripheral surface, so that it is structurally simple and obstruction such as jamming occurs. Is difficult to occur.

[Brief description of the drawings]

FIG. 1 is an overall cross-sectional view of a document supply apparatus according to the present description, which is partially omitted.

FIG. 2 is a partially enlarged cross-sectional view of the document supply device.

FIG. 3 is an enlarged view around a switchback roller of the document supply device.

FIGS. 4A and 4B are schematic explanatory diagrams of a document collection state. FIG.

FIG. 5 is a time sequence diagram of the document supply device.

[Explanation of symbols]

 G document X document reading section a circulation path b supply path c discharge path d switchback path 2 platen 4 feed stacker 5 feed roller 5a outer peripheral surface 6 discharge roller 7 discharge stacker 8 first transport direction switching means 9 second transport direction Switching means 10 Reversing roller 14 First register roller 15 Second register roller 21 Support plate

Claims (11)

[Claims] 1. A document supply device for an image forming apparatus, comprising: a paper feed stacker for loading a double-sided document; a discharge stacker for loading a double-sided document after reading; and a circulation path having a document reading position. A supply path for supplying a two-sided original from the paper supply stacker to the circulation path, a discharge path for discharging the two-sided original after reading to the discharge stacker, and a supply path or a lower part of the supply stacker. A switchback path for switching back and reversing the two-sided document, and provided at a connection portion between the circulation path and the switchback path, for switching a document conveyance direction to the circulation path or the switchback path. First transport direction switching means, provided at a connection portion between the circulation path and the discharge path, the circulation path or the discharge path Document feeder, characterized in that it comprises a second conveying direction switching means for switching the conveying direction of the document. 2. When reading only one side of a document, the first transport direction switching means guides the document to the circulation path,
The second transport direction switching means guides the document to the discharge path. When reading both sides of the document, the first transport direction switching means guides the document to the switchback path, and the second transport direction switching means guides the document to the switchback path.
2. The document supply device according to claim 1, wherein the conveyance direction switching unit guides the document after the one-side reading is completed to the circulation path, and guides the document after the both-side reading is completed to the discharge path. 3. The circulation path includes a first conveyance path from a connection part with the supply path to a connection part with the discharge path, and a connection path from a connection part with the discharge path to a connection part with the supply path. 3. The document feeding device according to claim 1, wherein the document feeding device includes a second conveyance path. 4. The paper feed stacker, the paper discharge stacker,
2. The switchback path according to claim 1, wherein the switchback path is located on the same side as the reading position.
The document supply device according to any one of claims 1 to 3, 5. The document feeding apparatus according to claim 1, wherein the sheet feeding stacker, the sheet discharging stacker, and the switchback path are arranged in a stack from the top. 6. The document supply apparatus according to claim 5, wherein the switchback path is provided in a space below the discharge stacker. 7. The switchback path according to claim 1, wherein a reversible reversible roller is provided in the switchback path, and the document is switched back by switching a rotation direction of the reversible roller. The document supply device according to 1. 8. The document feeder according to claim 7, wherein the reversible roller is configured such that a pair of rollers can be separated from each other, and separates when the document straddles the circulation path and the switchback path. 9. The document supply device according to claim 1, wherein a discharge roller rotatable in only one direction is provided in the discharge path. 10. The document feeder according to claim 1, wherein the circulation path is formed along an outer peripheral surface of one feed roller. 11. A paper feed stacker for loading a document, a discharge stacker for loading a document after reading, document reading means for reading an image of the document, and a guide for the document via the document reading means. A supply path for supplying double-sided originals from the paper feed stacker to the circulation path; a discharge path for discharging originals after reading to the discharge stacker; and the supply path or the supply path. A switchback path disposed below the paper stacker for switching back and reversing the original, and provided at a connection portion between the circulation path and the switchback path; First transport direction switching means for switching a transport direction, provided at a connection portion between the circulation path and the discharge path, wherein the circulation path or the An image forming apparatus comprising: a second conveying direction switching means for switching the conveying direction of the document to the output path.