JPH11349187A - Sheet separation device and picture image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent discharge of double fed sheets onto a tray especially for a sheet with printing in an overlapped state as they are. SOLUTION: When a head end of double fed sheets finished printing reaches a flapper 114 at a PI position through a fixing device 110, the flapper 114 revolves to a P2 position. Consequently, a sheet without printing is separated from a sheet with printing. The sheet with printing is guided by the flapper 114, carried by a carrier roller pair 111, reaches a discharge roller pair 112, and is discharge onto a paper discharge tray 113 by the discharge roller pair 112. The separated sheet without printing is discharged onto a paper discharge tray 116 by a discharge roller pair 115.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet separating apparatus used in an image forming apparatus (a printer, a copying machine, a facsimile, etc.) for forming an image on sheets fed one by one.

[0002]

2. Description of the Related Art FIG. 11 shows an overall configuration of a laser beam printer representing a conventional image forming apparatus.

Here, the overall configuration of the printer will be briefly described.

This printer has an external manual paper feeder 1
00 is provided, and the sheet S
Are fed one by one.

[0005] The sheets S stacked on the manual feed tray 101 are sequentially fed out from the uppermost sheet by a paper feed roller 102 rotating clockwise in response to the input of a print start signal from a host computer (not shown).

The sheet S fed by the paper feed roller 102 is separated one by one by a separation pad 103 of a high friction member which is in contact with the paper feed roller 102 at a predetermined pressure.

[0007] The sheet S fed out by the paper feed roller 102 and separated by the separation pad 103 is sent to the registration roller pair 104 in a rotation stopped state. In this case, it is checked whether or not the sheet S fed by the manual sheet feeder 100 behaves as specified by sheet detection means (here, a photo interrupter) 105 installed immediately upstream of the registration roller pair 104. It is performed using.

That is, if the sheet detecting means 105 detects the leading edge of the sheet at a predetermined timing, it is determined that the sheet S behaves as specified. However, when the sheet detecting unit 105 does not detect the leading edge of the sheet at a predetermined timing, it is determined that there is a sheet feeding abnormality. Then, in this case, the printing operation is stopped.

The sheet S, which behaves as specified, stops moving when a predetermined amount of loop is formed by the leading end of the sheet abutting the nip of the pair of registration rollers 104.
As a result, the skew state of the sheet S is corrected, and the sheet S in the correct posture is sent to the transfer unit.

On the other hand, a laser beam L emitted from a laser scanner 107 is irradiated onto a photosensitive drum 106 rotating in a clockwise direction via a return mirror 108. Thus, an electrostatic latent image is formed on the photosensitive drum 106, and the electrostatic latent image is developed by a toner developing device (not shown).

The laser scanner 107 emits a laser beam L based on image information sent from the host computer when a print start signal is input from a host computer (not shown).

The sheet S, which has been corrected for the skew state, has a pair of registration rollers 104 which starts rotating at a predetermined timing.
Is transferred to a transfer portion between the photosensitive drum 106 and the transfer roller 109. Then, the toner image on the photosensitive drum 106 is transferred by the transfer roller 109 to the sheet S passing through the transfer unit.

The sheet S to which the toner image has been transferred after passing through the transfer section is sent to the fixing device 110. Then, the toner image is heated and pressurized while passing through the nip of the fixing roller pair 110-1, and the unfixed toner image is fixed on the sheet surface.

The sheet S having passed through the nip of the pair of fixing rollers 110-1 and having been subjected to the fixing process is sent to the pair of discharge rollers 112 by the pair of conveying rollers 111, and the pair of discharge rollers 11
2, the paper is discharged onto the paper discharge tray 113.

[0015]

By the way, the image forming apparatus is provided with a sheet separating means (separating pad 103) for separating the sheets one by one as in the above-mentioned printer. Double feed may occur. This is, for example, a sheet stacking means (manual feed tray 101).
This is because when the sheets stacked on top of each other are in an electrostatic attraction state or in a state where fibers are entangled, the sheet separating means may not function sufficiently.

In the conventional image forming apparatus, the multi-fed sheet is discharged onto the discharge stacking means (discharge tray 113) after the image formation (printing) is completed while the multi-fed sheet remains. Therefore, the sheet on which the image has been formed and the unused white paper are stacked on the discharge stacking means in an overlapping state.

However, when filing or stapling a bundle of sheets stacked on the discharge stacking means, the user may be unaware that blank sheets are mixed in the work. In such cases, it took a great deal of time to remove blank paper from the sheet bundle.

The present invention has been made in view of the above circumstances, and separates an image-forming sheet from an image-forming sheet so that only the image-forming sheet is stacked on a predetermined discharge stacking means. It is an object of the present invention to provide a sheet separating device.

[0019]

SUMMARY OF THE INVENTION The present invention relates to a sheet separating apparatus for separating a non-image forming sheet from a plurality of image forming sheets conveyed in an overlapping state.

In order to achieve the above object, the present invention provides an overlapping state detecting means for detecting whether or not a plurality of image forming sheets are conveyed in an overlapping state, and a plurality of overlapping image forming sheets. A separating unit for separating the sheet without image formation from the sheet for use, and a control unit for driving the separating unit at a predetermined timing when the overlapping state detecting unit detects the overlapping state.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 shows the overall configuration of a laser beam printer (image forming apparatus) to which the present invention is applied.

In describing the structure of this printer, the same members as those of the above-described conventional printer (FIG. 11) are denoted by the same reference numerals, and those which do not change in structure and function are described. Omitted.

The printer checks whether sheets fed from the manual sheet feeder 100 are multi-fed, and if multi-fed, prints (toner image transferred) and no prints from the sheet. A function is provided for separating sheets (blank paper) and stacking only printed sheets on a predetermined discharge tray 113.

In this printer, whether or not the sheets fed from the manual sheet feeder 100 are multi-fed (confirmation of multi-feed) is determined by a sheet detecting means installed immediately upstream of the registration roller pair 104. (Overlapping state detecting means) 105 is performed. Separation of the non-printed sheet from the printed sheet is performed using a flapper (separating unit) 114 installed immediately downstream of the fixing device 110.

FIG. 2 shows a state in which a sheet fed from the manual sheet feeder 100 is double fed. here,
The feed roller 102 is the first sheet (top sheet)
S1 and the second sheet S2 are fed out. The second sheet S2 is shifted from the first sheet by a distance D1. This is because the separation pad 103 is provided on the second sheet S2.
This is because the frictional force is working.

The sheet detecting means 105 detects the leading edge and the trailing edge of the fed sheet S. The CPU (controller of the printer) 117 counts the time from when the sheet detecting means 105 detects the leading edge of the sheet to when it detects the trailing edge of the sheet. In the case of a sheet that has not been multi-fed, the count time matches the transport time (set value) set for each sheet size (transport direction size). However, in the case of a multi-feed sheet, the count time is lengthened by the deviation (D1) between the sheets S1 and S2, and a time difference X occurs between the count value and the set value (see FIG. 5). When the time difference X occurs, the CPU 117 determines that a double feed has occurred.

The flapper 114 for separating the non-printed sheet from the multi-feed sheet is rotatable up and down around a support shaft (rotary shaft) 114-1. The flapper 114 is rotated by driving a motor (stepping motor M1) 132 transmitted to the support shaft 114-1.

The initial position of the flapper 114 is a position P1 indicated by a solid line. If no double feed occurs, the flapper 114 is set at the P1 position. Further, in the case where the double feed has occurred, the standby is at the P1 position until the separation start point, and the separation operation is performed at P2 shown by an imaginary line.
Rotate to the position. Immediately after the flapper 114 reaches the P2 position, the drive is stopped, and the flapper 114 returns to the P1 position by the action of a return spring (not shown). In this case, a spring having a low spring force is used as the return spring.

If there is no double feed, the printed sheet after passing through the fixing device 110 is the flapper 114 located at the P1 position.
The sheet is guided to the conveyance roller pair 111, is sent to the discharge roller pair 112 by the conveyance roller pair 111, and is discharged onto the paper discharge tray (first stacking means) 113 by the discharge roller pair 112.

In the case where the multi-feed has occurred, the flapper 11 is set when the multi-feed sheet passes through the fixing device 110 as described later.
Reference numeral 4 rotates from the P1 position to the P2 position to separate the unprinted sheet from the printed sheet. As a result, only the printed sheet is transported to the transport roller pair 111. The non-printed sheet is discharged by a discharge roller pair 115 onto a discharge tray (second stacking unit) 116 dedicated to the non-printed sheet.

Next, referring to FIG. 3 and FIG.
The separating operation of No. 14 will be described in detail.

The flapper 114, which is on standby at the position P1 in FIG. 1, starts to rotate counterclockwise when the leading ends of the multi-feed sheets S1 and S2 slightly exit the fixing device 110. The leading end 114-2 of the flapper 114 that has started to rotate is shifted from the leading end of the non-printing sheet S2 by a distance D1 while the flapper 114 reaches the position P2 in FIG. It comes into contact with the back surface (the state shown in FIG. 3), and is scooped up to the position P2 (FIG. 4).
State). Thus, the unprinted sheet S2 is separated from the printed sheet S1.

Here, the timing at which the flapper 114 on standby at the P1 position starts to rotate for separation is at the leading end 114-2 of the flapper 114 in the middle of rotating to the P2 position. It is an essential condition to abut on the back surface of S1. Here, in order to satisfy this condition, the same timing is set for the sheet detecting unit 1.
The time t1 is set based on the time t1 required until the leading end of the sheet S1 with print detected at step S05 reaches the leading end 114-2 of the flapper 114 at the position P1 in FIG. Then, after the lapse of the time t1, the flapper 114 at the position P1 is driven when the time t2 has elapsed (the motor 132
ON) (see FIG. 5). Here, the time t2 is shorter than the time X of the shift amount D1 of the multi-feed sheets S1 and S2.

Here, the flapper 114 is P
The reason why the drive is stopped immediately upon reaching the second position is to prevent the flapper 114 from being a load for conveying the sheet S1 with print. Further, the reason why a spring having a weak spring force is used as the return spring of the flapper 114 is as follows.
This is to prevent 14 from becoming a transport load of the non-printed sheet S2.

In the case of the present printer, the multi-feed sheets S1, S2
Is fed, the unprinted sheet S2 is separated from the printed sheet S1 when passing through the fixing device 110, and the printed sheet S1 is a discharge tray 1 dedicated to the printed sheet.
13 and the non-printed sheet S2 is discharged onto the discharge tray 116 dedicated to the non-printed sheet, so that the non-printed sheet S2 can be filed together with the printed sheet S1 as in the related art. No stapling. <Second Embodiment> FIG. 6 shows the overall structure of another laser beam printer to which the present invention is applied.

In describing the structure of this printer, the same members as those of the printer shown in FIG. 1 are denoted by the same reference numerals, and a description of those which do not change in structure and function is omitted.

While the printer of FIG. 1 is a printer dedicated to single-sided printing, this printer is a printer capable of double-sided printing.

The present printer is provided with a re-conveying path 118 for conveying the sheet S having passed through the fixing device 110 to the registration roller pair 104 again.

An opening / closing member 119 for opening and closing the re-transport path 118 is provided at the entrance. The opening and closing member 119 is made of an elastic sheet material such as Mylar,
Normally, the inlet is open as shown.

In the re-conveying path 118, a plurality of conveying roller pairs 120 to 122 for conveying the sheet S are provided. Among them, the transport roller pairs 120 and 121 are configured to be able to correct the curl attached to the sheet S while transporting the same.

The transport roller pair 111 and the discharge roller pair 112 of this printer can be rotated forward and backward.

The above points are different from the printer of FIG.

Next, the operation of the present printer will be described.

In the single-sided print mode, when no double feed occurs, the flapper 114 is set at the position P1, and the transport roller pair 111 and the discharge roller pair 112 are in a normal rotation state.

The printed sheet S that has passed through the fixing device 110 pushes down the opening / closing member 119 (closes the entrance portion), and
The flapper 114 at one position is reached. Then, the sheet is guided by the flapper 114, conveyed by the conveying roller pair 111, and reaches the discharge roller pair 112. Then, the sheet is discharged onto the sheet discharge tray 113 by the discharge roller pair 112.

In the single-sided print mode, when double feed occurs, the flapper 114 is on standby at the position P1, and the transport roller pair 111 and the discharge roller pair 112 are in a normal rotation state.

The multi-feed sheet S that has passed through the fixing device 110
1 and S2 reach the flapper 114 at the P1 position while pushing down the opening / closing member 119. Thereafter, the flapper 114 at the position P1 rotates to the position P2. Thus, the unprinted sheet S2 is separated from the printed sheet S1.

The printed sheet S 1 is guided by the flapper 114, conveyed by the conveying roller pair 111, and reaches the discharge roller pair 112. Then, the sheet is discharged onto the sheet discharge tray 113 by the discharge roller pair 112.

On the other hand, the non-printed sheet S2 reaches the discharge roller pair 115, and is discharged onto the discharge tray 116 by the discharge roller pair 115.

When no double feed occurs in the double-sided print mode, the flapper 114 is set at the position P1, and the transport roller pair 111 and the discharge roller pair 112 are in a normal rotation state.

The sheet S with first-side print having passed through the fixing device 110 reaches the flapper 114 at the position P1 while pushing down the opening / closing member 119. And the same flapper 1
The sheet is guided by the feed roller 14, conveyed to a conveying roller pair 111, and further conveyed to a discharge roller pair 112.

When the trailing edge of the sheet S with printing on the first side, which is being conveyed, has passed the flapper 114, the pair of conveying rollers 111 and the pair of discharging rollers 112 are switched from normal rotation to reverse rotation. Thereby, the sheet S with the first surface printing
Is switched back, and the re-conveying path 118 is guided by the
Go in. When the trailing end of the sheet passes through the nip of the pair of conveying rollers 111, the pair of conveying rollers 111 and the pair of discharging rollers 112 are switched from reverse rotation to normal rotation.

The sheet S with first-side printing, which has entered the re-conveying path 118, is conveyed by the conveying roller pairs 120 to 122, and the registration roller pair 104 in the rotation stopped state again.
To reach. At this time, if the sheet detecting unit 105 does not detect the leading edge of the sheet at a predetermined timing, it is determined that there is a conveyance error, and the printing operation is stopped.

The sheet S on the first surface having reached the registration roller pair 104 finishes printing on the second surface in the same process as when printing on the first surface, and then finishes the fixing process.

The sheet S with the second printing surface that has passed through the fixing device 110 reaches the flapper 114 at the position P1 while pushing down the opening / closing member 119. And the same flapper 1
The sheet is guided by the feed roller 14, is conveyed to a conveying roller pair 111, and is discharged onto a discharge tray 113 by a discharge roller pair 112.

When double feed occurs in the double-sided print mode, the flapper 114 stands by at the position P1 and the transport roller pair 111 and the discharge roller pair 112 are in a normal rotation state.

The multi-feed sheet S that has passed through the fixing device 110
1, S2 reaches the flapper 114 at the P1 position while pushing down the opening / closing member 119. Thereafter, the flapper 114 at the position P1 rotates to the position P2. As a result, the sheet S1 with the first-side printing and the sheet S2 without the printing are printed.
Separate.

The unprinted sheet S2 is a discharge roller pair 115
And the discharge roller pair 115 causes the discharge tray 1
16 is discharged.

On the other hand, the sheet S1 with first-side printing is guided by the flapper 114, conveyed to the conveying roller pair 111, and further conveyed to the discharge roller pair 112. Then, when the trailing edge of the sheet passes through the flapper 114 at the position P1, the transport roller pair 111 and the discharge roller pair 112 are switched from normal rotation to reverse rotation.

As a result, the first-side printed sheet S1 is switched back, and enters the re-conveying path 118 while being guided by the flapper 114 with the previous sheet trailing end as the leading end. When the trailing end of the sheet passes through the nip of the pair of conveying rollers 111, the pair of conveying rollers 111 and the pair of discharging rollers 112 are switched from reverse rotation to normal rotation.

The first-side printed sheet S1 that has entered the re-conveying path 118 thereafter flows in the same manner as the first-side printed sheet S without the occurrence of double feeding, and finishes printing on the second side. After the processing, the sheet is discharged onto the sheet discharge tray 113.

In the case of this printer, when the multi-feed sheets S1 and S2 are fed in the single-sided print mode, the fixing device 11
At time 0, the unprinted sheet S2 is separated from the printed sheet S1 from the printed sheet S1, the printed sheet S1 is discharged onto the discharge tray 113 dedicated to the printed sheet, and the unprinted sheet S2 is discharged exclusively from the non-printed sheet. Since the sheet S2 is discharged onto the tray 116, the sheet S2 without printing is not filed or stapled together with the sheet S1 with printing unlike the related art.

In the double-sided print mode, the multi-feed sheet S
When the sheets S1 and S2 are fed, the sheets S1 having the first-side printing and the sheets S having no printing have passed when the sheet S has passed through the fixing device 110.
2, the unprinted sheet S2 is discharged onto a discharge tray 116 dedicated to the non-printed sheet, and the first-sheet printed sheet S1 is a discharge tray dedicated to the printed sheet after printing on the second side is completed. Since the sheet is discharged onto the sheet 113, unlike the related art, the sheet without printing S2 is not filed or stapled together with the sheet with printing S1.

Printing on the second surface can be reliably performed on the sheet S1 with first surface printing. Therefore, there is no need to perform printing on the first and second surfaces again as in the related art.

<Third Embodiment> FIG. 7 shows the overall structure of still another laser beam printer to which the present invention is applied.

In describing the structure of this printer, the same members as those of the printer shown in FIG. 6 are denoted by the same reference numerals, and the description of those which are not structurally and functionally omitted will be omitted.

Here, the operation of the present printer will be described to show the structural differences from the printer of FIG.

In the single-sided print mode, when no double feed occurs, the flapper 114 stands by at the P1 position, the flapper 124 is set at the P1 position, and the discharge roller pair 11
5, 125 are in the normal rotation posture.

The printed sheet S that has passed through the fixing device 110 moves toward the flapper 114 at the position P1 while pushing down the opening / closing member 119.
Shortly before reaching, the flapper 114 rotates to the P2 position. As a result, the printed sheet S1 is
It passes below and reaches the discharge roller pair 115.

Subsequently, the sheet S with print is guided by the flapper 124 at the position P1 and reaches the discharge roller pair 125, and is discharged onto the discharge tray (first stacking means) 126 by the discharge roller pair 125. You.

The flapper 124 has the same configuration as the flapper 114. Reference numeral 133 denotes a stepping motor for transmitting drive to the support shaft 124-1 of the flapper 124.

In the single-sided print mode, when there is a double feed, the flappers 114 and 124 stand by at the position P1 and the discharge roller pairs 115, 125 and 127 are in the normal rotation state.

The multi-feed sheet S that has passed through the fixing device 110
1, S2 pushes down the opening / closing member 119 and heads toward the flapper 114 at the P1 position, but immediately before the sheet leading edge reaches the flapper 114, the flapper 114 rotates to the P2 position. Thus, the multi-feed sheets S1 and S2 reach the discharge roller pair 115 under the flapper 114.

Subsequently, the multi-feed sheets S1 and S2 reach the flapper 124 at the position P1. Thereafter, the flapper 124 at the position P1 rotates to the position P2. Thus, the unprinted sheet S2 is separated from the printed sheet S1.

The printed sheet S 1 is guided by the flapper 124 and is driven by a discharge roller pair 125 to a discharge tray 126.
Discharged up. On the other hand, the unprinted sheet S2 is discharged by a discharge roller pair 127 to a discharge tray (second stacking means) 12.
8 is discharged.

When no double feed occurs in the double-sided print mode, the flappers 114 and 124 are set at the position P1, and the pair of transport rollers 111 and the pair of discharge rollers 115 and 125 are set.
Is in the normal rotation position.

The sheet S with first-side print having passed through the fixing device 110 reaches the flapper 114 at the position P1 while pushing down the opening / closing member 119. And the same flapper 1
14 and transported by the transport roller pair 111,
The transport path 123 moves upward in the substantially vertical transport path 123.

When the trailing end of the sheet S with first-side printing, which moves upward on the transport path 123, passes through the opening / closing member 119, the transport roller pair 111 switches from normal rotation to reverse rotation. As a result, the first-side printed sheet S is switched back, and enters the re-conveying path 118 while being guided by the flapper 114 with the previous sheet trailing end as the leading end. When the rear end of the sheet passes through the nip of the pair of conveying rollers 111, the pair of conveying rollers 111 is switched from reverse rotation to normal rotation.

The sheet S with the second-side print, which has passed through the fixing device 110, moves toward the flapper 114 at the position P1 while pushing down the opening / closing member 119. Rotate. As a result, the sheet S with second-side printing passes below the flapper 114 and reaches the discharge roller pair 115.

Subsequently, the sheet S with the second-side printing is guided by the flapper 124 at the position P1, and
25, and is discharged onto the discharge tray 126 by the discharge roller pair 125.

When double feed occurs in the double-sided print mode, the flappers 114 and 125 stand by at the P1 position, and the pair of transport rollers 111 and the pair of discharge rollers 115 and 127 are provided.
Is in the normal rotation position.

The multi-feed sheet S that has passed through the fixing device 110
1, S2 reaches the flapper 114 at the P1 position while pushing down the opening / closing member 119. Thereafter, the flapper 114 at the position P1 rotates to the position P2. As a result, the sheet S1 with the first-side printing and the sheet S2 without the printing are printed.
Separate.

The unprinted sheet S2 is a discharge roller pair 115
To the flapper 124 at the P1 position. At this time, the flapper 124 rotates to the P2 position just before the leading end of the sheet reaches the flapper 124. Accordingly, the non-printed sheet S2 reaches the discharge roller pair 127 under the flapper 124, and is discharged onto the discharge tray 128 by the discharge roller pair 127.

On the other hand, the sheet S1 with first-side printing is guided by the flapper 114, conveyed by the conveying roller pair 111, and moves upward on the conveying path 123.

When the trailing end of the sheet S1 on the first surface, which moves upward on the transport path 123, passes through the opening / closing member 119, the transport roller pair 111 switches from normal rotation to reverse rotation. As a result, the sheet S1 with the first-side printing is switched back, and the flapper 114 is switched from the rear end of the sheet to the front.
And enters the re-conveying path 118 while being guided by the guide. When the rear end of the sheet passes through the nip of the pair of conveying rollers 111, the pair of conveying rollers 111 is switched from reverse rotation to normal rotation.

The sheet S1 with the second-side print that has passed through the fixing device 110 goes to the flapper 114 at the position P1 while pushing down the opening / closing member 119. Rotate. As a result, the sheet S1 with second-side printing passes below the flapper 114 and reaches the discharge roller pair 115.

Subsequently, the sheet S1 with the second-side printing is P1
The sheet is guided by the flapper 124 at the position, reaches the discharge roller pair 125, and is discharged onto the discharge tray 126 by the discharge roller pair 125.

In the case of this printer, the sheet with the first-side print to be sent to the re-conveying path 118 is guided to the conveying path 123 which is in a substantially vertical state, and is switched back.
For this reason, even if the trailing edge of the first-side printed sheet moving upward on the transport path 123 may pass through the nip of the transport roller pair 111, the trailing edge of the sheet may be moved by its own weight to the nip of the transport roller pair 111. The transport roller pair 111
6 can be reliably performed, and the sheet transportability is further stabilized as compared with the printer of FIG.

<Fourth Embodiment> FIG. 8 shows a method for increasing the certainty of the timing at which the flapper 114 of each of the printers shown in FIGS. 1, 6, and 7 starts to rotate for separation.

Here, a reflection type photosensor (sheet leading end detecting means) 129 is attached to the flapper 114,
When the flapper 114 is at the position P1, the photo sensor 12
9, light is emitted toward the cover surface (reflection surface) of the fixing device 110. Reference numeral 129-1 denotes an optical path.

In such a configuration, the leading end of the sheet that has passed through the fixing device 110 always shields the optical path 129-1 immediately before reaching the flapper 114. That is, the photo sensor 129 is turned on to detect the leading edge of the sheet. The CPU 117 of the printer rotates the flapper 114 at the position P1 to the position P2 at the timing when the photosensor 129 is turned on.

In the method of setting the timing at which the flapper 114 starts to rotate based on the transport time in which the leading edge of the sheet will reach the flapper 114, the timing may be adjusted if the transport of the sheet is delayed due to some reason. However, when the timing is set based on the detection of the leading edge of the sheet as in this example, there is almost no deviation in the timing, and the reliability of the timing is improved.

FIG. 9 shows a preferred wiring method of the signal line (cable) 135 of the photosensor 129 attached to the flapper 114.

Here, the signal line 1 of the photo sensor 129 is used.
35 is drawn into the support shaft 114-1 using a hollow shaft, and is drawn out from one end of the support shaft 114-1. In addition,
The support shaft 114-1 is rotatably supported by the support members 134-1 and 134-2.

When the signal line 135 is wired as described above, the signal line 135 does not act as a load on the rotating flapper 114, and the flapper 114 rotates smoothly. <Fifth Embodiment> FIGS. 1, 6, and 7 show FIGS.
A method for increasing the certainty of the timing at which the flapper 114 of each printer starts rotating for separation (a method different from that in FIG. 8) will be described.

Here, the reflection mirror 1 is attached to the flapper 114.
31, and a reflection type photosensor (sheet leading edge detecting means) 130 is provided above the fixing device 110.
When the flapper 114 is at the P1 position, the photo sensor 13
Light is emitted from 0 toward the reflection mirror 131. Reference numeral 130-1 is an optical path.

In such a configuration, the leading end of the sheet that has passed through the fixing device 110 always shields the optical path 130-1 immediately before reaching the flapper 114. That is, the photo sensor 130 is turned on to detect the leading edge of the sheet. The CPU 117 of the printer rotates the flapper 114 at the position P1 to the position P2 at the timing when the photo sensor 130 is turned on.

[0098]

As described above, according to the present invention,
It is detected whether or not a plurality of image forming sheets are conveyed in an overlapped state. If the sheets are in an overlapped state, a sheet without image formation (blank sheet) is separated from a sheet with image formation by using a separating unit. Therefore, the sheet without image formation is not discharged in a state where the sheet with image formation overlaps the sheet with image formation.

Therefore, there is no need to file or staple an image forming sheet on which an image non-forming sheet overlaps.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a laser beam printer (image forming apparatus) to which the present invention is applied.

FIG. 2 is a cross-sectional view illustrating a state in which a multi-feed sheet is fed from a manual sheet feeder.

FIG. 3 is a cross-sectional view showing a state in which a separating operation of a multi-feed sheet has been started.

FIG. 4 is a cross-sectional view illustrating a state during a separating operation of the multi-feed sheet.

FIG. 5 is a timing chart showing the relationship between the timing at which the sheet detecting means detects the leading edge and the trailing edge of the sheet and the timing at which the driving of the flapper is turned on / off.

FIG. 6 is a sectional view showing the overall configuration of another laser beam printer to which the present invention is applied.

FIG. 7 is a sectional view showing the overall configuration of still another laser beam printer to which the present invention is applied.

FIG. 8 is a cross-sectional view showing a method for increasing the certainty of the timing at which the flapper starts rotating for separation.

FIG. 9 is a plan view showing a preferred wiring method of signal lines of a photo sensor attached to the flapper.

FIG. 10 is a cross-sectional view showing another method for increasing the certainty of the timing at which the flapper starts rotating for separation.

FIG. 11 is a cross-sectional view showing the overall configuration of a conventional laser beam printer.

[Explanation of symbols]

105 Sheet detecting means (overlapping state detecting means) 113, 126 Paper discharge tray (first stacking means) 114 Flapper (separating means) 114-1 Flapper support shaft 116, 128 Paper discharge tray (second stacking means) 117 CPU (control means, overlapping state detecting means) 129, 130 Reflection type photo sensor (sheet leading edge detecting means) 129-1, 130-1 Optical path S1 Sheet with printing (sheet with image formation) S2 Sheet without printing (no image formation) Sheet)

Claims (22)

[Claims] In a sheet separating apparatus for separating a non-image forming sheet from a plurality of image forming sheets conveyed in an overlapped state, it is determined whether or not a plurality of image forming sheets are conveyed in an overlapped state. Overlapping state detecting means for detecting, separating means for separating the non-image forming sheet from the plurality of image forming sheets in the overlapping state, and separating means at a predetermined timing when the overlapping state detecting means detects the overlapping state And a control means for driving the sheet separation device. 2. The image forming apparatus according to claim 1, further comprising: a first stacking unit for stacking a sheet with an image formed thereon and a second stacking unit for stacking a sheet without an image formed downstream of the separating unit. 2. The sheet separation device according to 1. 3. The sheet detecting unit detects the leading edge and the trailing edge of the image forming sheet being conveyed, and detects the trailing edge of the sheet from the time when the sheet detecting unit detects the leading edge of the sheet. 2. The sheet separating apparatus according to claim 1, further comprising: an overlap state determination unit configured to determine an overlap state based on a time up to a time point. 4. The sheet separating apparatus according to claim 1, wherein the overlapping state detecting unit detects the overlapping state at a stage before the image is formed on the image forming sheet. 5. The sheet separating apparatus according to claim 1, wherein the separating unit is a member that can rotate around a support shaft. 6. The sheet separating apparatus according to claim 5, wherein the member is a substantially triangular member having a front end side at an acute angle. 7. The sheet separating apparatus according to claim 5, wherein the member is rotated by driving transmitted to the support shaft. 8. In the process of rotating the member from the initial position (P1) to the predetermined position (P2), the leading end abuts on the back side of the preceding image forming sheet and scoops the image forming sheet. The sheet separating apparatus according to claim 5, wherein a sheet without image formation is separated from a sheet with image formation by raising the sheet. 9. When the member is rotated to a predetermined position (P2), the driving is stopped and the initial position (P
The sheet separating apparatus according to claim 8, wherein the apparatus returns to 1). 10. The sheet separating apparatus according to claim 9, wherein an urging spring having a weak spring force is used as the return unit. 11. The sheet separation apparatus according to claim 1, wherein the separation unit separates a sheet without image formation after an image is formed on the image formation sheet. 12. The control means drives the separation means at a time when a time from when the sheet detection means detects the sheet front end to when the sheet front end reaches the separation means elapses. The sheet separating apparatus according to claim 3, wherein 13. The sheet separating apparatus according to claim 1, further comprising a sheet leading end detecting unit that detects a sheet leading end immediately upstream of the separating unit. 14. The sheet separating apparatus according to claim 13, wherein the sheet leading end detecting means is a sensor that emits light blocked at a sheet leading end. 15. The sheet separating apparatus according to claim 14, wherein the sensor is provided on the separating unit, and emits light toward an upstream side of the separating unit. 16. The sheet separating apparatus according to claim 15, wherein a signal line of the sensor is passed through a hollow shaft that is a rotation center of the separating unit. 17. The sheet separating apparatus according to claim 14, wherein the sensor is provided near immediately upstream of the separating unit, and emits light toward the separating unit. 18. The sheet separation apparatus according to claim 13, wherein the control unit drives the separation unit when the sheet front end detection unit detects the sheet front end. 19. An image forming apparatus for forming an image on an image forming sheet fed one by one, comprising the sheet separating apparatus according to claim 1. Description: Image forming apparatus. 20. An image forming apparatus for transferring a toner image to an image forming sheet fed one by one and fixing and discharging the toner image transferred to the image forming sheet. 19. An image forming apparatus, comprising: the sheet separating apparatus according to any one of claims 18 to 18. 21. The image forming apparatus according to claim 19, further comprising a double-sided image forming mode for forming an image on both sides of the image forming sheet. 22. An image forming apparatus according to claim 19, wherein said overlapping state detecting means detects an overlapping state before transferring the toner image onto the image forming sheet, and after the fixing of the toner image is completed, said separating means causes said image forming sheet to change from the image forming sheet to the non-image forming sheet. 21. The image forming apparatus according to claim 20, wherein: