JPH0459575A - Image forming device - Google Patents

Abstract

PURPOSE:To carry out a both-side copying or a multiple copying to a long size sheet by using a conveying route as a sheet refuge to turn over or to resup ply the sheet concurrently, or forming the sheet refuge in a clearance space in an image forming device. CONSTITUTION:A sheet P on which an image is formed by an image forming means 11 is conveyed to resupply means 45 to 47 passing through the parts 43, 82a, and 82b of a conveying route, as it is, or after turning over the front surface and the rear surface in turnover members 76, 79, and 80, and then resup plied to the image forming device 11 by the resupply means 45 to 47, and a multiple copying or a both-side copying is carried out. In this case, the refuge of the sheet P made at the turnover members 76, 79, and 80, and the resupply means 45 to 47 is carried out in the parts of the conveying route 43, 82a, 82b, and 73, or in a clearance space in an image forming device 1. Consequently, a multiple copying or a both-side copying can be carried out to a long size sheet P.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to image forming apparatuses such as copying machines and laser beam printers. Regarding paper routes.

(El) Prior Art In recent years, due to the wide range of originals to be copied and the wide range of purposes used by users, there has been a demand for color image forming apparatuses. There is an increasing desire to form images in various colors such as blue.

In response to this request, a plurality of developing devices are housed, the developing devices are filled with developers of various colors such as red, blue, and green, and the developing devices of each color are automatically replaced according to the usage request of the user. Devices have been proposed that are capable of providing multicolored reproduced images.

A copying machine 1 is shown in FIG. Document placement glass 2
The original 2 placed on the surface a is illuminated by a lamp 3, and its light image is projected onto a photosensitive drum 11 by an optical system consisting of reflective mirrors 4, 5, 6°7, 8.9 and a zoom lens 10.
be led upwards. The lamp 3, the mirror 4, and the mirror 5.6 each move at a predetermined speed in the direction of the arrow to scan the original 2.

On the other hand, since the photosensitive drum 11 is also rotated in the direction of the arrow after its surface is uniformly charged by the primary charger 12, electrostatic latent images corresponding to the original image are sequentially formed on the surface of the photosensitive drum 11. Ru. Color toner (
For example, a color developing device 13c containing toner (for example, green) and a black developing device 14 containing black toner are provided. These developing devices 13c.

14 is movable in the direction of the arrow, and approaches the photosensitive drum 11 to visualize the electrostatic latent image on the photosensitive drum 11 according to a desired color image.

In the case of this figure, since the color developer 13c is far away and the black developer 14 is close, a black image is formed on the photosensitive drum 11. This image is transferred onto the sheet P by the transfer charger 15. Thereafter, the photosensitive drum 11 reaches a cleaner 16, where residual toner on the drum surface is removed, and the process returns to the next copying process.

The sheet P is fed as follows and the original image is copied. There are the following three methods for feeding the sheet P into the copying machine 1. In the first method, sheets are loaded in a cassette 18 and fed to a pair of rollers 20 by a feed roller 19. roller vs 2
0 is such that when multiple overlapping sheets of transfer paper 17 are fed in, the top paper is separated and fed into the device.After passing through this pair of rollers 20, the sheet P is guided Board 21
．． 22, feeding roller pair 50, guide plate 52, 53.51
It reaches the registration roller 23 via. In the second method, the paper is loaded in the cassette 24 and fed into the roller pair 2 by the feed roller 25.
Sent to 6. The roller pair 26 has the same function as the previous roller pair 20, and after the sheet P passes through the roller pair 26, it passes through the guide plates 27 and 28, the feeding roller pair 50, and the guide plate 5.
It reaches the registration roller 23 via 2.53.51. The registration rollers 23 start rotating at a timing such that the developed image on the photosensitive drum 11 and the sheet P match, and feed the transfer paper to the surface of the photosensitive drum 11 via an upper transfer guide 31 and a lower transfer guide 32.

As described above, the image on the surface of the photosensitive drum 11 is transferred to the transfer paper by the transfer charger 15, the transfer paper is separated from the drum surface by the separation charger 33, and then transferred to the heating roller 35a and the pressure roller 35b via the conveying section 34. and is sent to a fixing device 35 having a. Sheet P heated and pressurized by the fixing device 35
The upper image is fixed as a permanent image, and the sheet P is sent to the first discharge roller 36, then the flapper 37, the flapper 3
8, the sheet P reaches the second ejection roller 39, and is then ejected to the outside of the copying machine 1. In Fig. 0, the flapper 38 is shown blocking the path of the sheet P, but this flapper 38 Since it is made to be rotatable in the direction of the arrow, when the sheet P passes, it is pushed up by the leading edge of the sheet P, and takes a retracted position with respect to the sheet P, so there is no hindrance to the passage of the sheet P. does not occur.

Furthermore, the basic conveyance operation of the sheet p during zero-order duplex and multiple copying, in which duplex and multiple copying are possible in this copying machine 1, will be shown.

When the duplex copying operation is instructed to the copying machine 1, the original image is transferred and fixed on one side of the sheet P in the same way as the basic operation described above, and the sheet P is sent to the second ejection roller 39 and ejected from the machine. Then, the trailing edge of the sheet P is detected by the paper detection mechanism consisting of the detection lever 40 and the optical sensor 41, and after a certain period of time (that is, the time until the trailing edge of the sheet P passes the flapper 38), the trailing edge of the sheet P is detected. 2 discharge roller 39
starts reversing and feeds the sheet P into the copying machine 1 again, and this time, the sheet P passes through the flapper 38, the left slope of the flapper 37, the guide plate 42, and then the guide plates 43 and 44a, with the rear end first. .

It is sent to the roller 45 via the 44b10-ra 100.

Thereafter, the sheet P passes through the roller 46 and refeed roller 47.
reach. At this point, the paper refeed roller 47 is stopped, and after the sheet P completely hits this roller 47, the rollers 45 and 46 also stop. The sheet P then waits for copying operation to the other side. When a copy signal for the other side is issued, the paper refeed roller 47 starts rotating and the guide plate 4
8. Feed the sheet P to the registration roller 23 via 49. The operation after the sheet P reaches the registration rollers 23 is the same as the basic operation described above, and the sheet P on which the image has been copied on the other side is finally transferred to the second ejection roller 3.
9, it is ejected from the aircraft.

On the other hand, in the first copying operation when the copying machine 1 is instructed to perform a multiple copying operation, the original image is transferred and fixed onto the sheet P in the same manner as the basic operation. In the case of multiple copying, the flapper 37 is in the state shown by the broken line. Then, the sheet P is sent out by the first discharge roller 36 with the front end first, sent to the guides 42 and 43 along the right slope of the flapper 37, and then sent to the roller 45 via the guides 44a and 44b and the roller 100. Sent. Thereafter, the sheet P passes through the roller 46 and reaches the refeed roller 47. These rollers 45, 46
．． 47 are provided with guide plates 90a, 90b, and 90e. The rear end of the sheet P?detection lever 40, optical sensor 4
1, and after a predetermined period of time has elapsed, the flapper 37
returns to the position indicated by the solid line. Then, when the second copy signal is issued, the paper refeed roller 47 starts rotating, and the movement of the sheet P at this time is the same as in the case of double-sided copying. The sheet P on which the image has been copied a second time on the same side is finally discharged out of the apparatus by the second discharge roller 39.

When creating a multicolor copy image using such a device, basically the image formation is repeated for each color (developing unit) used. To obtain the image, first form an image on the sheet P in green (developing device 13C), guide the sheet P to the image forming section again via the paper feed conveyance path of section A, then replace the developing device, and form an image in red (developing device 13C). An image is formed in the developing device 13B), and an image is formed in blue (developing device 13D) in the same manner, thereby completing a three-color copy image.

Next, the means for making two or more copies will be explained.

FIG. 15 shows the refeed roller 4 from the roller 100 in FIG. 14.
7 is a control block diagram of rollers and sensors arranged in the paper refeed path 101 up to 7. FIG.

In FIG. 15, 45M, 46M, and 47M are motors that respectively drive the four rollers 45, 46 and the paper refeed roller 47, and are connected to each roller by a drive transmission means (not shown) of a gear train.

The motors 45M, 46M, and 47M use stepping motors and rotate by a predetermined angle according to the number of pulses sent from the control circuit 60, and can also be controlled in forward and reverse directions by the control circuit 60. Reference numeral 61 is a keyboard for specifying the number of copies, duplex mode, multiplex mode, etc., and instructing the control circuit 60 to start copying.

62.90a, 90b, 90c, 64.65 are sheets P
The guide 64 is formed with a recess 64A that receives a loop of the sheet P that is formed when the leading edge of the sheet hits the refeed roller 47.

66 and 67 are sensors that detect the presence or absence of a sheet.

Next, the operation of storing a plurality of sheets P in the paper refeed path 101 will be explained using the flowchart shown in FIG.

When the duplex or multiple copy mode is set using the keyboard 61 and a copy start is instructed, the sheet P, which is taken out from the cassette 18 or 24 and has an image formed on one side by the photosensitive drum 11, is fed to the roller 100 as described above. It's coming. After the predetermined time t1 required from when the leading edge of the sheet P is detected by the sensor 67 to when the leading edge of the sheet reaches the nip of the roller pair 45 in (step Sl) in FIG. 16, the motors 45M and 4'6M are started. (steps S2 and S3), and rotates the bamboo motors 45M and 46M for a required predetermined time t to transport the sheet P a preset distance ρ after it is pinched by the pair of rollers 45 (step S4), and when t2 elapses. Rear motor 45M, 46
M stops (step S6, see FIG. 17), and the rotation of the roller pair 45, 46 is controlled by the control circuit from the motor 45M,
It can also be controlled by the number of pulses sent to 46M. That is, the roller pair 45 can be similarly adjusted by sending the number of pulses corresponding to the rotation angle of the motor 45M necessary to convey the sheet P a predetermined distance β after the leading edge of the sheet P hits the nip of the roller pair 45. 45 can be controlled. Note that the reason why the motor 46M is also operated together with the motor 45M is that when the number of sheets P is large, the tip of the bundle of sheets P is moved by the roller 4.
This is because it will be held between the two.

Next, in step S6, it is determined whether the set number of sheets has been loaded or not, and if the stacking has not been completed, (step S6)
Return to l). Then, when the next sheet P is conveyed and reaches the roller pair 45, the roller pair 45 conveys the sheet P by a predetermined amount β, similar to the previous one. As a result, the two sheets are overlapped in a shifted state. By performing this operation on a plurality of sheets P, the sheets can be stacked one after another with the sheets shifted by β as shown in FIG.

Regarding the operation when refeeding the next stacked sheet P for the second image formation of double-sided or multiple copying, Chapter 19
This will be explained based on the flowchart shown in the figure.

When a start is instructed by the keyboard 61, the motor 4
Rotation of 5M and 46M is started, the stacked sheets are sent to the refeeding roller 47, and the leading edge of the first sheet P□ hits the nip portion of the roller pair 47 (step 521).
, the first sheet P.

When the rear end passes through the roller pair 46, the motors 45M, 4
6M is stopped (step 524) (FIG. 20), this timing is determined by the elapsed time t3 since the leading edge of the first sheet P is detected by the sensor 66 (step 522) (step 523), and then Step S2
5, the motor 47M is driven to rotate the roller pair 47 and feed the first sheet P. Since the heated sheet P is held between the stopped roller pair 45 or 46, its movement is prevented and separation is performed.

At this time, the rollers 45 and 46 remain stopped and hold the remaining bundle of sheets P, so only the first sheet P1 is fed, and this operation is repeated for the number of stacked sheets. By repeating this, sheets can be fed sequentially.

When forming an image twice on one sheet P by double-sided copying or multiple copying, after the second image formation is performed by the above method, the first discharge roller 36 and the second The paper is discharged out of the apparatus via the discharge roller 39, and the series of copying operations is completed.

Next, a case where images are formed three or more times on each sheet, such as three- or four-color composite copying on a plurality of sheets P, will be explained with reference to the flowchart of FIG.

The operations follow the flowchart in FIG. 16 until the first image formation is performed and stacking is performed as shown in FIG. 18.

Next, when a command to start is given via the keyboard 61, it is determined in step S31 whether or not this is the second to last image formation. In the case of the last image formation, the sheet P is re-fed according to the flow chart shown in FIG. 19, and the sheet P on which the image has been formed is ejected by the ejection roller 39. Note that whether or not the last image formation is to be performed is determined by the control circuit 6 using the keyboard 61.
The number of repetitions of image formation input to 0 and the control circuit 6
The determination is made by comparing the number of repeated image formations that have been completed with a count of 0. If it is not the last image formation, that is, if the sheet is sent to the paper re-feed path again after image formation and image formation is repeated again, the process advances to step S32, and the entire stack of sheets is sent out by the roller pair 45, 46. After the predetermined time t3 has passed since the leading edge of the first sheet P1 passed the sensor 66 (step 833.34), the leading edge of the first sheet P hits the nip of the refeeding roller pair 47, and the trailing edge When the roller pair 45 and 46 are completely removed, the roller pair 45 and 46 are stopped at step 535.
), the re-feeding roller pair 47 is rotated in the normal direction to feed the lowest sheet P.
Only 1 is sent out (step 536).

Next (step 537), the roller pair 45, 46 is reversed to send the entire remaining stack of sheets upstream m (in the direction of the arrow in FIG. 22). Then, when the tip of the uppermost sheet (P) reaches a position downstream of the roller pair 45 by a predetermined amount II (Fig. 22) (step 838), the roller pair 45.46
In step 539), the process waits for the re-fed sheet P to finish forming an image and return to the re-feed path. Step 5310) The tip of P passes through the sensor 67.
, after reaching the nip portion of the roller pair 45 after t1 time (step 5311), the roller pair 45 and 46 are moved to t2.
Rotate by a predetermined amount after a certain period of time (steps 5312 and 5313
, 5314), the returned sheet is stacked with the returned sheet shifted upstream by ρ with respect to the topmost sheet. This operation is repeated as many times as the number of sheets P that were loaded at the beginning (
At step 8315), the second image formation on all the transfer sheets is completed, and they are again stacked in a crooked state as shown in FIG. Then, as described above, by sequentially feeding the first sheet P of this bundle of sheets P, image formation can be performed for the third time.

Furthermore, if the sheet P on which the third image formation has been completed is guided again to the roller 45 in the same manner as described above, the fourth image formation is also possible. Therefore, it is possible to perform N-time image formation on one sheet P or on a plurality of sheets P.

(c) Problems to be solved by the invention However, in the above conventional example, as shown in FIG.
Since the guide plates 90a, 90b, and 90c, which are paper refeed trays, are short due to restrictions on the length of the copying machine 1, when stacking sheets P, when stacking the next sheet P on top of the stack of sheets P, If the length of the guide plate 90a is not L2 or L8>■, 1-ρ with respect to the length Ll of the sheet P, the sheets P cannot be stacked. Therefore, there is a drawback that the length of the copying machine 1 becomes long for a long sheet P such as A3 size sheet P.

Further, even if the guide plate 90a is directed downwardly of the copying machine 1, there is a drawback that the height of the copying machine 1 increases.

Furthermore, as shown in FIG. 14, when the copying machine 1 does not have a sheet evacuation section for reversing the sheet and performs double-sided copying, a portion of the sheet P is removed by the second discharge roller 39 at one time. It is evacuated outside the copying machine 1.

At this time, if an operator or the like accidentally grabs a part of the sheet P that has been evacuated, there is a drawback that it may cause a paper jam.

Therefore, in the present invention, a sheet evacuation section used when reversing and refeeding a sheet is also used as a sheet transport path, or is formed in a gap inside the image forming apparatus, so that the sheet on which an image is being formed can be removed from the image forming apparatus. It is an object of the present invention to provide an image forming apparatus that prevents the image forming apparatus from coming out (7), prevents the apparatus from increasing in size, and reduces costs.

(d) Means for Solving the Problems The present invention has been made in view of the above-mentioned circumstances, and for example, as shown with reference to FIGS.
an image forming means (11) for forming an image on the image forming means (11);
Conveyance path (43, 82a, 82b, 73, 9
9b, 99c, 48) and paper refeeding means (45, 46, 4
7), a sheet reversing unit (76, 79, 80) located upstream of the sheet refeeding means (45, 46, 47) and for reversing the sheet (P), In an image forming apparatus (1) comprising a sheet retracting section (24, 72, 73) for retracting a rear end portion of the sheet (P) in the conveyance direction when reversing and refeeding, the sheet retracting section (24°72.73) is part of the conveyance path (43,82
a, 82b, 73), or is formed in the gap space (B) in the image forming apparatus (]).

Further, a part of the sheet retracting section (24, 72, 73) is also used as a paper feeding cassette (24).

Further, the sheet refeeding means (25, 26, 27) transports the sheets (P) on which images have been formed and has been transported by a required amount in the forward and reverse directions, and stacks them by shifting them by a predetermined amount (I2). A stacking section (4) conveys a stack of stacked sheets (P).
5, 46), and a refeeding section (46, 47) that refeeds the first sheet (PL) of the bundle of sheets (P) that has been conveyed.
).

(f) Function Based on the above structure, the sheet (P) on which an image has been formed by the image forming means (11) can be directly or
76, 79, 80), the paper is turned upside down, passes through part of the conveyance path (43, 82a, 82b), and then is transferred to the refeeding means (45).
, 46, 47) and the refeeding means (45, 46, 47).
47) to re-feed the paper to the image forming means (11),
Perform multiple or double-sided copying on sheet (P), at this time,
A part of the conveyance path (43, 82a, 43, 82a, 82
b, 73) or in the gap space (B) within the image forming apparatus (1).

Further, the sheet is evacuated onto the paper feed cassette (24).

Further, in the paper refeeding means (45, 46, 47), the sheet (P) on which image formation has been completed is conveyed by a required amount in the forward and reverse directions by the stacking section (45, 46), and is conveyed by a predetermined amount (I2) at a time. The staggered and stacked stack of sheets (P) is conveyed to the paper refeeding section (46, 47), and the stacked sheets (P) are transported to the paper refeeding section (46, 47).
As a result, the first sheet (P, ) of the bundle of sheets (P) is re-fed.

Note that the above-mentioned symbols in parentheses are illustrative and do not limit equivalent configurations.

(f) Example The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a copying machine 1 embodying the present invention.

Components having the same structure and function as those in FIG. 14 showing the conventional example are given the same reference numerals to avoid duplication of explanation.

The difference from FIG. 14 is that the shape of the guide plate 42 is changed to a guide plate 71, and the guide plate 44a is removed.
A lower guide 72 is provided in the gap space B of the copying machine 1,
Continuing from the guide plate 71, it is curved and extends above the left end of the cassette 24.

Further, the guide plate 90a shown in FIG. 14 is extended and transformed into an upper guide plate 73 facing the guide plate 72.

Further, a wedge-shaped guide plate 75 is provided opposite to the upper and lower guide plates 72 and 73, and a roller pair 76 is interposed between the guide plate 71 and the lower guide plate 72, and is opposed to the guide plate 75.
In addition, a guide plate 77 extending between the roller pairs 76 and 100 is provided.

Furthermore, the flappers 37, 38 are also removed and a flapper 78 is provided in their place, and a flapper 79, 80 is provided below between the guide plates 43 and 71. An auxiliary flapper 81 that is made of plastic or the like and can be easily bent is erected at the lower end of the flapper 78, and is located at the downstream end of the guide plate 82a below the guide plates 82a, 82b near the downstream side of the roller pair 100. An auxiliary flapper 83 similar to the auxiliary flapper 81 is provided, and normally the guide plate 8
The downstream ends of 2a and 82b are closed.

The operation of the above-mentioned flapper etc. will be explained below when explaining the operation.

Next, the operation of this embodiment will be explained.

First, when performing multiple copying on the sheet P, after forming an image in the same way as single-sided copying, as shown in FIG. 2, the sheet P1 is The roller pair 10 is guided along the guide plate 43 by the flapper 80 (position indicated by the dotted line in FIG. 1).
0, the sheet P1 is guided in the direction of the guide plates 82a, 82b, and is further guided by the pair of rollers 45, 46, 47. When the rear end of the sheet P1 passes through the auxiliary flapper 83, as shown in FIG. The pair 45, 46.47 is reversed, and the sheet P1 is fed between the guide plates 73.75, with a predetermined amount ρ remaining at the front end of the sheet P, as shown in FIG.
make it stop. Then, when the second sheet P2 is brought into contact with the nip portion of the roller pair 45, the roller pair 45.46.
47, the sheets P t overlap by a predetermined amount
, P a is conveyed to the right, and when the rear end of the sheet P2 passes through the auxiliary flapper 83, the roller pairs 45, 46, 47
is reversed, the sheets P, , P2 are fed between the guide plates 73° and 75, and the front end of the second sheet Pa is moved by a predetermined amount I2.
Stop it in the same state.

By repeating such operations, a bundle of sheets P shifted by a predetermined amount C is formed as shown in FIG.

Then, after the leading end of the first sheet (Pt) hits the nip of the roller pair 47 and the rear end passes through the roller pair (see FIG. 6), the roller pair 45 is stopped, and the roller pair 46.47 is rotated in the normal direction, and only the first sheet P1 not held between the pair of rollers 45 is conveyed again to the image forming section to form a double-edge image.Then, the first sheet P1 is transferred to the pair of discharge rollers. Discharge by 39.

The second sheet P is also discharged in the same manner. This operation is repeated to perform double copying on all sheets P.

Next, when double-sided copying is to be performed on the sheet P, as shown in FIG. 7, after forming an image on one side, the sheet is guided along the guide plate 43 by the flapper 78 (position indicated by a dotted line in FIG. 1). It is guided along the lower guide plate 72 by the flapper 80 (the position indicated by the solid line in FIG. 1) and the flapper 79 (the position rotated clockwise from the position indicated in FIG. 1).
After the rear end of the sheet P1 passes through the flapper 80, the roller pair 76 is reversed to move the sheet P, as shown in FIG.
Guided along the guide plate 77 according to position 1) indicated by a solid line in FIG.
．． 47, and is conveyed by the pair of rollers 45, 46, 47 until the rear end of the sheet P1 passes through the auxiliary flapper 83, and is then reversed and moved to the guide plate 7 as shown in FIG.
3, and when the rear end of the sheet P1 remains on the roller pair 45 by a predetermined amount β, the roller pair 45 is stopped.

Then, wait for the second sheet P8 to be conveyed in the same manner as described above,
As shown in FIG. 10, when the rear end of the second sheet P2 contacts the nip portion of the roller pair 45, the roller pair 45
, 46, 47 are rotated in the forward direction, and after the front end of the second sheet P8 passes through the auxiliary flapper 83, the roller pairs 45, 4
6° 47 is reversed, and when the front end of the second sheet P remains a predetermined amount β, it stops and waits for the next sheet P. Repeating this operation, the predetermined amount β is left as shown in Figure 5. A bundle of sheets P shifted one by one is formed. The subsequent operations are the same as those for multiple copying described above.

As explained above, the guide plate 72 provided in the gap B between the sheet conveyance path and the interior of the copying machine 1 when refeeding sheets.
．． 73, by forming a sheet reversing section during double-sided copying and a sheet evacuation section when refeeding sheets, it is possible to handle long sheets without increasing the length or height of the copying machine. It also enables multiple and double-sided copying, which can significantly reduce costs.

Further, as explained in FIG. 6, when the first sheet P passes through the roller pair 45, the first sheet PL is re-fed by normal rotation of the roller pair 46 and 47. In contrast to the conventional proposal in which the first sheet P1 is re-fed after the first sheet P1 passes through the roller pair 46, the re-feed distance to the registration rollers 23 is increased. By doing so, it becomes possible to downsize the copying machine 1.

Next, another embodiment will be described with reference to FIG. 11.

In this embodiment, after single-sided copying is performed on the sheet P, the sheet P is discharged with the image side facing downward.

The sheet P that has been copied on one side is guided along the guide plate 43 by the flapper 78 (the position indicated by the dotted line in FIG. 1).
Flapper 80 (position indicated by solid line in Figure 1), 79 (first position)
(the position rotated clockwise in the figure) lower guide 72
along the rear edge of the sheet P or the auxiliary flapper 81.
When the sheet P passes through, the roller pair 76 is reversed and the sheet P
is guided to a pair of discharge rollers 39 with the rear end leading, and is discharged from the machine by this pair of discharge rollers 39.

Next, still another embodiment will be described with reference to FIG. 12.

In this embodiment, the tips of the upper and lower guide plates 73 and 72 of the embodiment shown in FIG. 1 are extended to the bottom surface 85 of the copying machine 1.

By doing so, it is possible to retract the sheets more smoothly without steps than by forming a retraction section on the cassette 24.

Next, another embodiment will be described with reference to FIG.

In this embodiment, the present invention is applied to reversing and discharging sheets of a single-sided copying machine.

A flapper 86 having an auxiliary flapper 87 is provided between the pair of paper discharge rollers 36 and 39, and the pair of rollers 36, 39
A pair of guide plates 91.92 are provided extending downward from the cassette 24 and having tips thereof.
A pair of rollers 93 is provided between the rollers 92 .

As a result, the sheet P, which has an image copied on one side and is discharged from the pair of paper discharge rollers 36, is conveyed along the guide plates 91 and 92 at the position indicated by the dotted line on the flapper 86, and the rear end of the sheet P is When the roller pair 93 passes the auxiliary flapper 87, the roller pair 93 reverses and the flapper 86
becomes the posture shown by the solid line.

The sheet P is reversed by the reversing roller pair 76 with the trailing end as the leading edge, and the sheet P is discharged by the discharge roller pair 39 with the image surface facing the back surface.

In this way, while keeping the length of the copying machine 1 short, the sheet P can be reversed and discharged without temporarily retreating outside the machine when the sheet P is reversed.

(g) As described in detail, according to the present invention, the sheet evacuation section for reversing and refeeding sheets is also used as a conveyance path, or is formed in a gap space within an image forming apparatus. double-sided printing and printing on long sheets without increasing the size of the device.
In addition to enabling multiple copies, it also prevents sheets in the middle of image formation from retreating outside the device, which can significantly reduce costs and prevent paper jams caused by an operator accidentally grabbing a sheet during image formation. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view of a copying machine showing an embodiment of the present invention, FIG. 2 is a cross-sectional front view showing its multiple copying state, and FIG.
4 and 5 are cross-sectional front views showing the state of each stage of stacking sheets during multiple copying, FIG. 6 is a cross-sectional front view showing the sheet re-feeding state, and FIGS. 7 to 10 are 11 is a sectional front view showing the state of each stage of double-sided copying, FIG. 11 is a sectional front view showing another embodiment, FIG. 12 is a sectional front view showing still another embodiment, and FIG. 13 is another embodiment. 14 is a sectional front view of a conventional copying machine, FIG. 15 is a block diagram of its paper refeeding section, FIG. 16 is a flowchart showing its sheet stacking operation, and FIG. 17 is its location. FIG. 18 is a cross-sectional front view showing the sheet stacking state, FIG. 19 is a flowchart showing the sheet refeeding operation, and FIG. 21 is a sectional front view showing a state in which the trailing edge has passed through the sheet conveying means, FIG. 21 is a flowchart for refeeding sheets when forming images for three or more copies in a conventional copying machine, and FIG. 22 is a diagram showing the location of the refed sheet. FIG. 23 is a cross-sectional front view showing a standby state for stacking with a fixed amount of displacement, and FIG. 23 is a cross-sectional front view showing a retracted state when refeeding paper. 1... Image forming device (copying machine) 11... Image forming means (photosensitive drum) 24... Cassette. 24.72.73--Sheet retraction part (cassette, guide plate) 43.82a, 82b, 73.99
b, 99c, 48... Conveyance path (guide plate) 4
3, 82a, 82b, 73-part of conveyance path (guide plate) 45,46.47... paper refeeding means (roller pair), 45.46-... stacking section,
46.47... Paper refeeding section (roller pair) 76
．． 79.80... Sheet reversal section (roller pair, flapper) B... Gap space, ρ... Predetermined amount, P.
...Sheet, P, ...First sheet

Claims (1)

[Scope of Claims] 1. An image forming means for forming an image on a sheet, a conveyance path and a paper refeeding means for refeeding the sheet on which the image is formed to the image forming means, and the paper refeeding means. a sheet reversing section located on the upstream side of the means for reversing the sheet, and a sheet retracting section for retracting the rear end of the sheet in the conveyance direction when reversing and refeeding the sheet. In the image forming apparatus, whether the sheet evacuation section also serves as a part of the conveyance path;
Alternatively, an image forming apparatus characterized in that it is formed in a gap space within the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein a part of the sheet evacuation section is also used as a paper feed cassette. 3. The paper refeeding means transports the sheets on which images have been formed and has been transported by a required amount in forward and reverse directions, and stacks them by shifting them by a predetermined amount, and also includes a stacking section that transports a bundle of stacked sheets. The image forming apparatus according to claim 1, further comprising: a paper refeeding unit that refeeds the first sheet of the bundle of sheets that has been conveyed.