JPH05155496A - Running passage switching mechanism for sheet - Google Patents

Abstract

PURPOSE:To discharge a sheet, processing, such as perfect printing, of which is completed, to the outside as rapidly as possible, in a running passage switching mechanism for a sheet effective to a perfect printing device wherein after printing is applied on the surface of a sheet, such as an ordinary sheet, the sheet is turned over and conveyed to a transfer part again, and a toner image is transferred to the back also and fixed. CONSTITUTION:In a device wherein a sheet running in a one-way through rolling forward of forward reverse rollers 16... is run in a reverse direction through reversing of the forward reverse rollers 16... and enters a different conveyance passage and in this way, a running passage for the sheet is switched, the forward reverse rollers 16... are set so that a velocity of periphery during reversing is increased to a value higher than that during running forward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prints on one side (front side) of a sheet such as plain paper, then turns the sheet over and transfers it to the transfer section again, and transfers the toner image on the back side. The present invention relates to a sheet path switching mechanism that is effective for a double-sided printing device that is fixed.

[0002]

2. Description of the Related Art FIG. 5 is a side view of a conventional double-sided printing apparatus. Reference numeral 1 denotes a photosensitive drum, and an exposure unit 2, a developing unit 3, a transfer unit 4, a cleaner 5, and a uniform charging unit 6 are arranged in this order on the outer circumference thereof in a clockwise direction. When the photosensitive drum 1 reaches the exposure unit 2 after being charged by the uniform charger 6 with the uniform charger 6, the information light 8 scanned by the optical system unit 7 is exposed.
The electrostatic latent image is formed by irradiating the surface. Toner is adhered to the electrostatic latent image by the developing device 3, and the toner image is transferred to a sheet such as plain paper at the position of the transfer device 4, and then the cleaner 5 removes the residual toner and electric charge, and the toner is again removed. Move to the position of the charger 6.

On the other hand, when a sheet such as plain paper is fed from the paper cassette 9, it passes through the paper feed path 10 and the alignment roller.
After reaching 11 and being aligned with the toner image on the photosensitive drum 1, the toner is transferred to the transfer device 4. Transfer device 4 illustrated in the figure
Consists of a transfer charger, and by corona discharge,
By applying a charge having a polarity opposite to that of the toner image to the sheet, the toner image on the photosensitive drum 1 is attracted to the sheet.

The sheet on which the toner image has been transferred is peeled from the photosensitive drum 1 by the peeling charger 12 and then transferred to the fixing device 13 where it is heated and fixed. That is, since the roller 13a on the photosensitive drum 1 side is a heat roller having a built-in heater, when the sheet having the toner image adhered thereto passes between the heat roller 13a and the pressure roller 13b, the sheet and the toner image are heated, Fixing is performed by melting and solidifying the toner image.

In the case of one-sided printing, the sheet on which the toner image is fixed passes between the impeller 14 and the discharge opposite roller 15, and the pair of forward / reverse rotation rollers 16 and 17 in the discharge conveyance path 24.
The paper is ejected to the paper ejection tray 19 by 18. In the case of double-sided printing, the trailing edge of the sheet is the impeller 14 and the forward / reverse rotation roller at the rear.
When it reaches the position between 16 and 16, the forward / reverse rotation rollers 16, 17, and 18 are reversed, so that the trailing edge of the sheet is guided between the impeller 14 and the opposing roller 20 for drawing, and the conveyance path for back side printing is provided.
The pair of discharge rollers 22 and 23 are transferred to the alignment roller 11.

During this time, since the sheet makes a U-turn, the sheet is transported between the fixing device 4 and the photosensitive drum 1 in a state where the front and back sides are reversed. When the back surface of the sheet reaches the photosensitive drum 1 side in this manner, the toner image on the photosensitive drum 1 is transferred to the back surface of the sheet. Next, after being transferred to the fixing device 13 and thermally fixed, it passes between the impeller 14 and the opposing roller 15, and is conveyed to the paper discharge tray 19 by the forward / reverse rotation rollers 16, 17, and 18.

[0007]

FIG. 6 is a side view showing a traveling state of each seat in the conventional apparatus. In the figure, S1 is the first sheet on which the back side is printed, and when the second sheet S2 whose one side has been printed is running in front of it, the first sheet S1 is printed on the back side and is discharged. Disturbs when ejected to the paper tray. That is, the transfer device 4
After the toner image is transferred and fixed, the first sheet
S1 is conveyed toward the discharge tray, but the second sheet S2 in front of it is conveyed in the discharge direction until the trailing edge of the sheet passes through the impeller 14, and then the forward / reverse rotation rollers 16, 17, 18 are By reversing the direction, the sheet moves backward toward the rear surface printing conveyance path 21.

Therefore, unless the second sheet S2 running forward has completely retracted into the back side printing conveyance path 21, the first sheet S1 which has completed double-sided printing is discharged and conveyed toward the discharge tray. Can't drive on road 24. So in reality,
The second sheet S2, which has been printed on one side, is completely retracted into the conveyance path 21 for back side printing, as shown by the chain line S2 ', and the leading end of the first sheet S1, which has been printed on both sides, faces the impeller 14. The second sheet S2 and the first sheet S1 can be sandwiched between the rollers 15.
Is sufficiently separated from. Therefore, when the second sheet S2 that has finished single-sided printing is present at the position shown by the solid line in the figure, the first sheet S1 for backside printing is at least a sheet length apart, and for far-side backside printing. Transport path
You are driving through 21.

As described above, in the conventional double-sided printing apparatus, since the distance between the sheets running inside the apparatus must be sufficiently separated, the printing speed is reduced and the double-sided printed first sheet S1 Discharge will be delayed. Moreover, if the first sheet S1 that has undergone double-sided printing is not ejected quickly and is running inside the device, the number of sheets staying inside the device increases, and it is eliminated when a paper jam occurs. Processing becomes complicated.

A technical problem of the present invention is to pay attention to such a problem, and to make it possible to discharge a sheet which has been subjected to double-sided printing or the like to the outside of the apparatus as soon as possible.

[0011]

FIG. 1 is a side view illustrating the basic principle of a seat path switching mechanism according to the present invention. According to the invention of claim 1, a sheet traveling in one direction due to the forward rotation of the forward / reverse rotation rollers (16 ...) Is caused to travel in the reverse direction due to the reverse rotation of the forward / reverse rotation rollers (16. In a device that switches the running path of a sheet by entering the road, the forward / reverse rotation roller (16 ...) Of the seat set so that the peripheral speed during reverse rotation is higher than the peripheral speed during normal rotation. It is a route switching mechanism.

In the sheet path switching mechanism of the first aspect, after printing on one side of a sheet such as plain paper, the sheet is turned upside down and transferred to the transfer section again, and the toner image is also transferred to the back side. It is especially effective for double-sided printing devices that fix by fixing. According to a second aspect of the present invention, the sheet path switching mechanism according to the first aspect is applied to a double-sided printing device, and the position of the forward / reverse rotation roller 16 at the rearmost end of the discharge / conveyance path 24 is set to
When the trailing edge of the second sheet S2 that has completed single-sided printing runs backward and passes toward the backside printing conveyance path 21, the leading edge of the first sheet S1 on which the backside printing is performed passes at least the fixing device 13. A sheet conveying mechanism that operates as described above is provided.

According to the third aspect of the present invention, the sheet running in one direction by the forward rotation of the forward / reverse rotation rollers (16 ...) As described above is reversed by the reverse rotation of the forward / reverse rotation rollers (16 ...). In a device for switching the traveling path of a sheet by causing the sheet to travel to a different conveying path, the impeller 14 having a large number of blade-shaped protrusions on the outer periphery is provided at the traveling path switching position of the sheet.
However, it is arranged in a free state with no opposing roller.

The rotational speed is set so that the peripheral speed of the outer circumference of the impeller 14 is higher than the retracting speed of the second sheet S2. Further, the sheet passes through the upper surface of the impeller 14 and travels in the discharge direction, and the second sheet S2 that is fed back by the forward / reverse rotation rollers 16, 17, 18 passes through the lower surface of the impeller 14 They are arranged in such a positional relationship that they travel on the transport path 21.

[0015]

In the invention of claim 1, the forward / reverse rotation rollers 16 ...
However, since the peripheral speed during reverse rotation is set to be higher than the peripheral speed during normal rotation, as shown in FIG. 1, printing on one side has already been completed, and printing operation on the back side is performed. When the second sheet S2 that interferes with the discharge of the first sheet S1 is present in the same conveyance path 24 as the first sheet S1, the second sheet
S2 is faster than the transport speed in its discharge direction
The second sheet S2, which runs backward in the direction of 21, can be evacuated and the front of the first sheet S1 can be evacuated from the first sheet conveying path 24 earlier than the second sheet S2 which hinders the traveling thereof.

As a result, the first sheet S1 whose back surface has been printed
And, by shortening the interval with the second sheet S2 running in front of it, the first sheet S1 that has finished back side printing can be ejected out of the device early, and by shortening the interval between each sheet, Printing speed is improved.

Further, by ejecting the first sheet S1 to the outside of the apparatus earlier in this way, the number of sheets staying inside the apparatus can be reduced, the frequency of paper jams can be reduced, and moreover, the paper jam can be reduced. It also facilitates processing when clogging occurs. That is, if the number of staying sheets in the apparatus is small, the frequency of paper jams is reduced accordingly, and even if paper jams occur, their positions can be easily found, and the work of removing jammed sheets becomes easy.

According to a second aspect of the present invention, in the sheet path switching mechanism according to the first aspect, there is provided means for minimizing the sheet interval in the sheet conveying path, and the position of the forward / reverse rotation roller 16 at the rearmost end of the discharge conveying path 24. When the rear end of the second sheet S2 that has completed single-sided printing passes toward the rear surface printing conveyance path 21, the front end of the first sheet S1 operates so as to pass at least the fixing device 13. Since the second sheet S2 is provided with the mechanism, the second sheet S2 can be reliably retracted to the back surface printing conveyance path 21, and then the first sheet S1 can promptly enter the ejection conveyance path 24 and be ejected early.

According to a third aspect of the present invention, the impeller in a free state having no opposing roller at the traveling path switching position of the sheet.
14 are provided. Therefore, the discharging / conveying speed of the first sheet S1 and the retracting speed of the second sheet S2 can be changed.

In the conventional apparatus shown in FIGS. 5 and 6, the impeller is
Opposite roller 15 for discharging and opposite roller for retracting on both sides of 14
Since there is 20, the sheet travels between the impeller 14 and the counter roller 15 in the discharge direction, and travels between the impeller 14 and the counter roller 20 in the retreat direction.

Therefore, for example, when the leading edge of the first sheet S1 is running between the impeller 14 and the counter roller 15, the trailing edge of the second sheet S2 is running between the impeller 14 and the counter roller 20. In such a case, the transport speed in the discharge direction and the transport speed in the retreat direction must be the same. Moreover,
In order to make the retracting and conveying speed higher than the sheet discharging and conveying speed, it is necessary to switch the rotation speeds of the impeller 14 and the facing rollers 15 and 20, which complicates the structure and control.

On the other hand, as in the present invention, the opposing roller
By eliminating 15 and 20 and leaving the impeller 14 in a free state, and further rotating so that the peripheral speed of the outer periphery of the impeller 14 is higher than the retracting speed of the second sheet S2, the high speed of the second sheet S2 It is possible to make the retreat conveyance speed of the second sheet S2 faster than the discharge conveyance speed of the first sheet S1 without hindering the retreat.

That is, the peripheral speed of the impeller 14 is the second seat S2.
If it is slower than the evacuation traveling speed of the second seat S2, the impeller 14 acts as a braking force for the evacuation traveling of the second seat S2.
Since the evacuation traveling speed is faster than the evacuation traveling speed, there is no fear that the evacuation traveling speed is reduced by the braking action. Also, the impeller 14
Even when the sheet rotates at a speed higher than the conveying speed of the first sheet S1, the conventional opposed roller 15 does not exist and the vehicle travels on the impeller 14, which hinders stable traveling of the first sheet S1. There is no such thing as coming.

Furthermore, since the trailing edge of the second sheet S2 is hit against the side of the other conveying path 21 by the impeller 14 rotating at a high speed, the second sheet S2 surely and at a high speed the side of the other conveying path 21. Will be guided to. As a result, the second sheet S2, which interferes with the ejection of the first sheet S1, can be retracted to another transport path 21 earlier, in combination with the higher evacuation traveling speed of the second sheet S2.

[0025]

EXAMPLES Next, examples of practical use of the seat track switching mechanism according to the present invention will be described. FIG. 2 is a side view showing an example in which the sheet path switching mechanism of the present invention is applied to a double-sided printing apparatus, and the same parts as those of the conventional apparatus shown in FIG.

The impeller 14 includes an opposed roller 15 shown in FIG.
It doesn't have 20 and is free. Then, the peripheral speed of the impeller 14 is driven at a high speed so as to be higher than the speed at which the second sheet S2 retreats from the discharge conveyance path 24 to the back side printing conveyance path 21. The impeller 14 in the present invention is
Although it does not have a facing roller, it has a pair of transport rollers 25 near the impeller 14 in the back surface printing transport path 21.

Forward / reverse rollers 16 and 1 in the discharge conveyance path 24
7 and 18 are linked by a gear mechanism, a timing belt, a chain, etc. so as to interlock with each other, and the sheet is conveyed in the discharge direction by forward rotation, and the reverse side conveyance path 21 by reverse rotation.
Retreat inside. When the sheet is conveyed in the discharge direction by forward rotation, the peripheral speed of each of the forward / reverse rotation rollers 16, 17, and 18 is the same as the sheet discharge / transport speed or the passage speed of the fixing device 13.

Further, in the case of retreating and conveying to the reverse side printing conveyance path 21 by reverse rotation, the peripheral speed of each of the forward / reverse rotation rollers 16, 17 and 18 becomes about twice as fast as during normal rotation, and the reverse side printing conveyance path 21
Each transport roller 25, 22, 23 in 21 is also a forward / reverse roller 1
It is driven at the same peripheral speed as that of the reverse rotation of 6, 17, and 18. The peripheral speed of the impeller 14 is slightly higher than the peripheral speed at the time of reverse rotation.

The forward / reverse rotation of the forward / reverse rollers 16, 17, 18 is switched by a sensor arranged between the fixing device 13 and the impeller 14.
The position of the sheet is detected at 26, and the detection signal is input to the control unit.

FIG. 3 is a side view showing the operation of the seat path switching mechanism by the impeller 14, which is (1) → (2) → (3) →
The sheet is conveyed in the order of (4). Heat roller 13 of fixing device 13
a is disposed on the photosensitive drum 1 side and has a pressure roller 13
b is arranged facing each other. The fixing device 13 and the discharge conveyance path 24
An impeller 14 is provided at a branch position between the rear surface printing conveyance path 21 and the rear surface printing conveyance path 21.

That is, when the sheet passes over the upper surface of the impeller 14 and is conveyed to the discharge conveyance path 24, and when the second sheet S2 is retracted from the discharge conveyance path 24 and retracted to the back side printing conveyance path 21, It passes through the lower surface of the impeller 14 and is sandwiched by the conveying rollers 25 next to the impeller 14.

Now, in (1), when the second sheet S2 on which single-sided printing is performed is running from the fixing device 13 toward the discharge / conveyance path 24, the forward / reverse roller in the discharge / conveyance path 24 is used.
16, 17, and 18 are rotating in the normal direction, and the second sheet S2 is the discharge conveyance path.
Transported to 24. At this time, the second seat S2 is
However, since the impeller 14 is rotating in the traveling direction of the second sheet S2 and the peripheral speed thereof is faster than the conveying speed of the second sheet S2, the traveling of the second sheet S2 is impeded. There is no such thing.

When the sensor 26 detects that the rear end of the second sheet S2 has passed the position of the sensor 26, the detection signal is input to the control unit, and the rear end of the second sheet S2 detects the sensor 26. When a predetermined time has passed after passing, the positional relationship is such that the rear end of the second sheet S2 has passed the center of the impeller 14 as shown in (2). Therefore, the rear end of the second sheet S2 is slid downward by the rotating impeller 14 and is guided to the back surface printing conveyance path 21 side as shown by the broken line. Moreover, since the impeller 14 is rotating at a high speed, the trailing edge of the sheet is instantly directed to the back surface printing conveyance path 21 side.

At this point, the forward / reverse rollers 16, 17, 18 in the discharging / conveying path 24 reversely rotate according to the control signal from the control section, and further rotate at a higher speed than in the discharging / conveying path. The second sheet S2 guided to the 21 side is fed into the rear surface printing conveyance path 21 at a higher speed than when traveling in the discharge direction. Then, as shown in (3), it is sandwiched by the next conveying roller 25 of the impeller 14 and is conveyed at a high speed in the backward direction by the conveying rollers 25, 22, 23 in the rear surface printing conveying path 21.

When the rear end of the second sheet S2 passes under the impeller 14, the sheet interval is set so that the front end of the first sheet S1 on which the double-sided printing is performed reaches the upper surface of the impeller 14. However, the leading edge of the first sheet S1 is detected by the sensor 26, and when the detection signal is input to the control unit and a predetermined time has elapsed, the forward / reverse rotation rollers 16, 17, 18 are controlled by the control signal.
Is switched to the forward rotation direction. Moreover, the normal rotation speed at this time is the same as the transport speed of the first sheet S1. As a result, even after the first sheet S1 enters the discharge / conveyance path 24, the first sheet S1 travels in the discharge / conveyance path 24 at the same speed and is discharged to the discharge tray.

In the above embodiments, the backside printing conveyance path
Each of the transport rollers 25, 22, 23 in 21 may be rotated at all times, or may be controlled so as to be rotated only while the second sheet S2 is traveling in the backside printing transport path 21.

In the apparatus of the illustrated embodiment, the second sheet S2 which has been subjected to the one-sided printing is smoothly and at a higher speed, the conveying path 21 for the back side printing.
The impeller 14 and the backside printing transport path so that
A downhill is formed between the conveyance roller 22 and the middle of 21.
That is, the tilt frame 29 is connected to the base 27 via the support shaft 28.

When the apparatus is in operation, the frame 29 is inclined, the impeller 14 is present at the upper end of the frame 29, and the conveying roller 22 is present at the lower end thereof. Therefore, the second sheet S2 retracted from the discharge conveying path 24 is conveyed. Since the action of sliding down by its own weight occurs in combination with the conveying force of the rollers 25 and the like, the second sheet S2 can be more quickly retracted.

When a paper jam occurs in the backside printing conveyance path 21, the tilt frame 29 can be tilted in the direction of the arrow around the support shaft 28 to make the tilt frame 29 horizontal and open the inside. It is easy to remove the jammed sheet.

FIG. 4 is a time chart showing the operation of each part in the seat path switching mechanism of FIG. Now, set the peripheral speed of the fixing roller to 133 mm / sec and the peripheral speed of the impeller 14 to 257 mm / sec, and drive them by the main motors. The peripheral speed of the forward / reverse roller 16 is 0 → ± 627 mm / se
c, that is, stop, drive in the forward direction at 627 mm / sec, drive in the reverse direction at 627 mm / sec, and drive with a dedicated forward / reverse rotation motor. The transport roller 25 in the transport path 21 for back side printing is set to a peripheral speed of 0 → ± 627 mm / sec and is driven by a dedicated back side motor. The signals controlling these four operations are emitted from the sensor 26.

A. Now, at the time a when the sensor 26 detects the leading edge of the sheet conveyed by the fixing roller at 133 mm / s, the sensor 26 is turned off.

B. The forward / reverse rotation motor starts rotating 400 msec after point a, and the forward / reverse rotation roller starts 419 msec later.
Set the peripheral speed of 16… to 133 mm / s.

C. After 1,100 msec from the time point a (when A4 size paper is fed horizontally), the forward / reverse rotation motor is set to the forward / reverse rotation roller 16
Accelerate the speed from 133mm / s to 627mm / s in 41msec. 1,100 msec after the time point a is enough time for the trailing edge of the A4 horizontal sheet to pass through the fixing device 13.

D. 1,185 msec after the time point a, the forward / reverse rotation motor drives the forward / reverse rotation roller 16 ... from the peripheral speed of 627 mm / s to 133 mm / s.
Then, decelerate over 41 msec.

E. When the paper passes the sensor 26 while being conveyed by the forward / reverse roller 16 ... at 133 mm / s, the sensor
26 turns on.

F → f '. After 0 msec from time point e, the forward / reverse rotation motor decelerates from 133 mm / s to 0 mm / s over 19 msec.

F '→ g. While the forward / reverse rotation rollers 16 are stopped (270 to 19 msec), the impeller 14 directs the trailing edge of the paper toward the conveyance roller 25 of the rear surface printing conveyance path 21.

G. After 270 msec from the time point e, the forward / reverse rotation motor turns the forward / reverse rotation roller 16 ... to -133 mm / s for 19 ms.
Accelerate with ec. That is, it is reversed. Then, the sheet whose rear end is directed toward the transport roller 25 is sent to the transport roller 25 by the reverse rotation of the forward / reverse rotation rollers 16.

H. After 370 msec from the time point e, the rear surface motor accelerates the carry roller 25 from 0 to 133 mm / s for 19 msec. After this acceleration is completed, 133
The paper sent at the conveyance speed of mm / s reaches the conveyance roller 25, and the forward / reverse rotation roller 16 ...
Sent at a speed of 33mm / s.

J. After 570 msec from the time point e, the forward / reverse rotation motor and the back surface motor have the forward / reverse rotation rollers 16 ...
25 over 41msec, -133mm / s → -627mm / s,
Accelerate from 133mm / s to 627mm / s.

As described above, in this embodiment, when the paper is retreated from the discharge conveyance path 24 toward the back side printing conveyance path 21, the forward / reverse rotation rollers 16 ... I try to evacuate in time. Further, as described in the above item c, the sheet is conveyed at high speed after the trailing edge of the sheet has passed through the fixing device 13, and the staying time of the sheet in the apparatus is shortened.

In each of the embodiments, the heat roller type is illustrated as the fixing device, but it goes without saying that the present invention can be applied to an apparatus having a flash fixing device at the position of the fixing device 13.

[0053]

As described above, according to the present invention, since the second sheet S2 retreats to another conveying path 21 at a higher speed than when the sheet is being discharged, the second sheet S2 is placed in front of the first sheet S1. Even if it exists, the second sheet S2 is quickly withdrawn from the discharge conveyance path 24, and does not hinder the discharge traveling of the first sheet S1.

Therefore, the second sheet S2 can be discharged earlier than the first sheet S1, and as a result, the staying time of the first sheet S1 in the apparatus can be shortened, so that the sheet staying in the apparatus can be shortened. Therefore, even if a paper jam occurs, the elimination process becomes easy.

Further, since the preceding second sheet S2 is swiftly retracted from the discharging and conveying path 24, the interval between the preceding second sheet S2 and the double-sided first sheet S1 can be shortened, Since it is not necessary to provide an interval longer than the sheet length as in the conventional case, the printing speed can be increased.

[Brief description of drawings]

FIG. 1 is a side view for explaining the basic principle of a seat path switching mechanism according to the present invention.

FIG. 2 is a side view showing a double-sided printing apparatus that implements the sheet path switching mechanism of the present invention.

FIG. 3 is a side view showing a seat path switching mechanism and its operation.

FIG. 4 is a time chart showing the operation of each part in the seat traveling path switching mechanism of FIG.

FIG. 5 is a side view of a conventional double-sided printing device.

FIG. 6 is a side view showing a traveling state of a seat in a conventional device.

[Explanation of symbols]

 1 Photosensitive drum 4 Transfer device 13 Fixing device 13a Heat roller 13b Pressure roller 14 Impeller 15,20 Opposing roller 16,17,18 Forward / reverse roller 19 Paper ejection tray S1 Double-sided first sheet S2 Single-sided printing The 2nd sheet that has been performed 21 Conveyance path for backside printing 22,23,25 Conveyor rollers in the conveyance path for backside printing 24 Ejection conveyance path 26 Sensor 27 Base 28 Spindle 29 Tilt frame

Claims (3)

[Claims] 1. A normal / reverse rotation roller (16 ...) Rotates the sheet traveling in one direction by the normal rotation of the normal / reverse rotation roller (16).
In a device that switches the traveling path of the sheet by causing the sheet to travel in the opposite direction by reversing the rotation of 16 ...), and to enter the other conveying path, the forward / reverse rotation roller (16 ... A seat path switching mechanism characterized by being set to be faster than the peripheral speed of time. 2. The forward / reverse rotation rollers (16 ...) Are disposed in the discharge / conveyance path (24), and the position of the forward / reverse rotation roller (16) at the rear end of the discharge / conveyance path (24) is set to one side. When the trailing edge of the second sheet (S2) that has completed printing runs backwards toward another conveyance path and passes, the leading edge of the first sheet (S1) should pass at least the fixing device (13). The sheet path switching mechanism according to claim 1, further comprising an operating sheet conveying mechanism. 3. A sheet running in one direction by the forward and reverse rotation rollers (16 ..
In a device that switches the traveling path of the sheet by traveling in the opposite direction by reversing the rotation direction of 16 ... ) Is arranged in a free state with no opposed rollers, and the rotation speed is set so that the peripheral speed of the outer circumference of the impeller (14) is higher than the retracting speed of the second sheet (S2). The fixed sheet has passed the upper surface of the impeller (14) and has run in the discharge direction, and the second sheet (S2) fed back by the forward / reverse rotation rollers (16) is the blade. A seat path switching mechanism, which is arranged in such a positional relationship that it passes through the lower surface of the vehicle (14) and travels to another transport path (21).