JPH028172A - Sheet transfer device - Google Patents

Abstract

PURPOSE:To prevent the damage of a picture image face by separating a preceding sheet by stopping the driving of a transfer means when the preceding sheet of the sheet group superposed by sliding its tip part is separated from the transfer means, in the sheet transfer device of a copying machine, etc. CONSTITUTION:The sheet group Sn superposed by sliding in order the tip part in the transfer direction is fed to a feeding means 31 by being interposed by a transfer means 29. When a preceding sheet S1 reaches the feeding means 31 and further is passed through the transfer means 29, the passing of the preceding sheet S1 is detected by a detection means 74, the transfer operation of the transfer means 29 is stopped, the transfer operation of the feeding means 31 is started and the preceding sheet S1 is transferred by separating from the other sheet. The sheet group Sn is fed to the transfer means 31 in order from the preceding sheet S1 and whenever the sheet is passed through the transfer means 29 the transfer operation of the transfer means 29 is stopped, yet the transfer operation of the feeding means 31 is started and it is separated and transferred one by one.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a sheet conveying device for conveying sheets of paper or the like in image forming apparatuses such as copying machines and laser beam printers. , or when stacking images on the same surface, the sheets are stacked on the sheet re-feeding section with their leading edges sequentially shifted, and are then separated one by one and re-feeded to the image forming section. The present invention relates to a suitable sheet conveying device.

(B) Conventional technology Conventionally, in an image forming apparatus such as a copying machine, when images are to be formed on both sides of a desired number of sheets or on the same side, the sheet with an image formed on one side is once placed in the apparatus. - The sheets are stored in a provided intermediate tray, and the sheets are separated one by one from the intermediate tray and re-feeded to the image forming section.

On the other hand, when refeeding sheets from the intermediate tray mentioned above, a group of stacked sheets shifted one by one in a stepwise manner is conveyed to the refeed roller at a constant speed to refeed the preceding sheet. A sheet conveying device has been proposed in which the sheet is separated from other sheets by the re-feeding roller each time it reaches the feeding roller (Japanese Patent Laid-Open No. 58-17837).
(See Publication No. 3). The publication also discloses a double feeding prevention means that can reliably separate and feed sheets in the sheet conveying device described above, such as providing a gate or a brake member to prevent double feeding of sheets, or In this case, a pad that presses against the refeeding roller, a reversing roller that is driven in the opposite direction to the refeeding roller, and the distance between the roller that conveys the stacked sheets to the refeeding roller and the refeeding roller are reduced. It describes matters such as setting the length to be slightly shorter than the length in the conveyance direction of the sheet.

(C) Problem to be Solved by the Invention By the way, the sheet conveying device described above can reliably separate and refeed the sheets one by one using the double-feed prevention means, but these double-feed prevention means If the separation member is installed, the device will require a lot of effort, and when separating the sheets, the separation member may come into contact with the sheets or apply excessive pressure, which may rub the image surface of the sheet and disturb the image. There is.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a sheet conveying device that separates and conveys stacked sheets one by one without rubbing against other members by sequentially shifting the leading edge, thereby solving the above-mentioned problems. It is something to do.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned circumstances. For example, as shown with reference to FIGS. 1 and 8, the sheet (S) is A group of sheets that are shifted and overlapped (Sn
) is separated and transported one by one.1. In the sheet conveying device (19), the group of sheets (So) is held and
The conveying means (29) for conveying and the conveying means (29) located at a distance smaller than the length in the conveying direction of the sheet (S) downstream of the conveying means (29) and sequentially sandwiching and conveying the preceding sheet (Sl) of the sheet group (Sn). The preceding sheet (Sl) of the sheet group (Sn) to be held and conveyed by the feeding means (31) and the conveying means (29)
a detection means (74) for detecting the passage of the conveyance means (74); The apparatus is characterized by comprising a control means (C1) for controlling the conveyance operation of the feeding means (31) to be stopped and the conveyance operation of the feeding means (31) to be started.

(f) Effect Based on the above-described configuration, the stacked sheets (Sn) with their leading ends in the conveying direction sequentially shifted are held by the conveying means (29) and sent to the feeding means (31).

Then, when the preceding sheet (Sl) of the sheet group (Sr1) reaches the feeding means (31) and further passes through the conveying means (29), the detecting means (74) detects the preceding sheet ( The passage of the transport means (2) is detected and the transport means (2
The conveying operation of step 9) is stopped, and then the conveying operation of the feeding means (31) is started, and the preceding sheet (S,) is conveyed separated from the other sheets sandwiched by the stopped conveying means. . Then, the superimposed sheet group (Sn) is sequentially sent to the feeding means (31) starting from the preceding sheet (Sl), and each time a sheet passes through the transporting means (29),
The conveyance operation of step 9) is stopped, and the conveyance operation of the feeding means (31) is started to separate and convey the sheets one by one.

Note that the symbols in parentheses above are shown for reference and do not limit the configuration in any way.

(F) Embodiments Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

A copying apparatus 1 configured to perform multiple copies or double-sided copies on the same sheet has a main body 3 containing a copying section 2, as shown in FIG. The device body 3
A document placement table 4, a light source 5, a lens system 6, two cassettes 7a and 7b for accommodating a large number of sheets S, etc. are arranged, and a cylindrical photoreceptor is located approximately at the center of the main body 3 of the apparatus. The copying section 2 consisting of 8 etc. is arranged. Around the photoreceptor 8, two developing units 9a and 9b each containing toner of a different color are provided so that they can be set and reset by moving in the direction of the arrow, and a transfer charger 1 is also provided.
A zero and separation charger 11, a cleaner 12, and a -order charger 13 are provided. In addition, the cassette 7a,
Paper feed rollers 14a and 14b are arranged facing the paper feed roller 7b, and conveyance roller pairs 15a and 15b, and paths 16a and 16, respectively.
The sheet S is guided to a pair of registration rollers 17 via a roller b, and the sheet S is subjected to multiple copies or double-sided copies via a sheet refeeding section 19 disposed below the main body 3 of the apparatus. is guided by the registration roller pair 17. Further, a fixing device 20 is disposed at the rear of the conveyance device 18 following the separation charger 11, and a first ejection roller pair 21 normally transfers the sheet S to a second The paper is disposed to be discharged onto a tray or the like outside the machine via a pair of discharge rollers 22. A flapper 23 and an auxiliary flapper 24 are disposed between the first pair of discharge rollers 21 and the second pair of discharge rollers 22, and the sheet S discharged from the first pair of discharge rollers 21 is normally disposed. is conveyed along the upper side of the flapper 23 at the solid line position,
The paper is discharged to the outside of the machine by a second pair of discharge rollers 22 that rotate normally. At this time, the auxiliary flapper 24 is swung upward by the conveyance force of the sheet S, and based on this, the detection arm 25 is moved and the optical sensor 26 is activated.
Passage of the sheet S is detected.

On the other hand, during double-sided copying, the sheet S is partially ejected out of the machine by normal rotation of the second ejecting roller pair 22, as in the normal case, or the rear end of the sheet S is When the detection arm 2 leaves the auxiliary flapper 24,
5 and the optical sensor 26 actuate the second discharge roller pair 2.
2 is driven in the reverse direction, and the sheet S is thereby guided to the left side of the auxiliary flapper 24 and the flapper 23 to move along the path 27.
It is now being introduced to Therefore, during double-sided copying, the sheet S is introduced into the sheet refeeding section 19 for refeeding to the copying section 2 by the second discharge roller pair 22, the detection arm 25, the optical sensor 26, and the path 27. .

Further, when performing multiple copying, the flapper 23 is switched to the position shown by the broken line, and the sheet S discharged from the first discharge roller pair 21 is directly introduced into the path 27 by the guiding action of the right side of the flapper 23. There is. Therefore, during multiple copying, the first discharge roller pair 21, the flapper 23,
Then, the sheet S is transferred to the sheet refeeding section 19 through the path 27.
It is now being introduced to

In the sheet refeeding section 19, a pair of introduction conveyance rollers 28 is disposed at the upstream portion, and a pair of conveyance rollers 29 and a pair of small size conveyance rollers 30 which rotate in both forward and reverse directions are disposed approximately at the center. Further, a pair of refeed rollers 31 is arranged downstream.

Note that the interval I21 between the introduction conveyance roller pair 28 and the conveyance roller pair 29 is the minimum length in the conveyance direction, and a slight margin α is set so that sheets S and n can be conveyed.

=LH1n-α, and the distance f22 between the small-sized conveyance roller pair 30 and the refeed roller pair 31 is set to n2=Lff1in-β, taking into account a slight margin β, and further between the conveyance roller pair 29 and The distance a3 between the refeeding roller pair 31 is set to Q3=L-□-β so that the largest sheet L□8 in the conveyance direction can be conveyed.

Then, the pair of introducing conveyance rollers 28 are arranged at the front and back of the main body
Drive roller 28a and driven roller '2 supported between plates
The drive roller 28a is driven in synchronization with the device main body 3 by a drive source (not shown), so that the device main body 3 always rotates in the direction of the arrow during operation. It should be noted that a detection arm 32a and a photodetection element 32 are installed immediately before the introduction conveyance roller pair 28.
A sheet detection sensor 32 is arranged. As shown in FIG. 2, a U-shaped arm 28c with a radius r or a drive mechanism (not shown) is attached to the drive roller 28a so as to be swingable about the axis of the roller 28a, and its length is a. is selected so that it can engage even the smallest size sheets.

Further, as shown in detail in FIG. 3, the conveyance roller pair 29 includes a drive roller 29a supported between the front and rear side plates of the main body;
It consists of an upper roller 29b which is vertically movable and rotatably supported by a shaft between the same side plates and is pressed against a drive roller 29a by a spring 33 hooked to a bearing. The drive roller 29a and the upper roller 29b are connected to a gear 34 and an idler gear 35.3 fixed to the drive roller 29a.
6. A gear train consisting of a gear 37 fixedly attached to the upper roller 29b connects the upper roller 29b so that the circumferential speeds of the two rollers are equal. Rotational connectivity is maintained. Further, the drive roller 29a is connected via a gear 39 to a drive pulse motor 38 that rotates forward and backward in response to a signal from the control unit C, and can rotate forward and backward according to the rotation of the motor 38, and the amount of rotation thereof. is controlled by control section C.

The small-sized transport roller pair 30 is composed of a drive roller 30a and an upper roller 30b, and the drive roller 30a is supported between the front and rear side plates of the main body, like the drive roller 29a of the transport roller pair 29, and is fixed to the drive roller 30a. By meshing with the provided manual gear 40 and the gear 39 provided on the drive pulse motor 38, the transfer roller pair 29 is rotated in the same direction and at the same circumferential speed as the drive roller 29a. Further, the upper roller 30b of the small size conveyance roller pair 30 is supported on an arm 41.41 rotatably disposed on the axis of the upper roller 29b of the conveyance roller pair 29.
Driving force is transmitted by a gear 43 fixed to the upper roller 30b through a gear 37 fixed to the upper roller 30b and an idler gear 42 pivotally supported to the arm 41, and the driving force is transmitted to the upper roller 30b at a constant speed. It is configured to rotate. Further, a balance spring 44 whose one end is fixed to the main body 3 of the apparatus is hung on the arm 41. The arm 41 is pulled by a balance spring 44 and stopped at a position where it abuts an upper stopper.
The two rollers 30a and 30b of No. 0 do not contact each other and are spaced apart from each other by about 2 mm. Furthermore, the balance spring 44
On the opposite side are the link 46 of the solenoid 45 and the arm 41.
A spring 47 is provided to connect the upper roller 30b of the small size conveying roller pair 30 by the operation of the solenoid 45.
It is configured such that it can be pressed against the drive roller 30a.

Further, as shown in FIG. 1, an upper guide plate 48 and a lower guide plate 49 are arranged between the introduction conveyance roller pair 28 and the conveyance roller pair 29, and the upper guide plate 48 is arranged between the introduction conveyance roller pair 28 and the conveyance roller pair 29. The sheet S that has passed through 28 is guided to a pair of transport rollers 29. Furthermore, one end of the lower guide plate 49 extends below the drive roller 28a of the pair of introduction conveyance rollers 28, and forms a retraction section 50 below the drive roller 28a. A groove 49a having a radius r and through which the arm 28c passes is provided so as not to interfere with the movement.

Further, as shown in FIGS. 4 and 5, the refeed roller pair 31, which is movable in the axial direction and has the function of correcting the position of the sheet in a direction perpendicular to the conveying direction, is provided with a pair of refeed rollers 31 that are in pressure contact with each other. It consists of a roller 31a and an upper roller 31b. The upper roller 31b and the lower roller 31a are connected to the front and rear side plates 3 of the apparatus main body 3 via bearings 52 and 52, respectively.
a and 3b, and is rotatably and slidably supported by a spring 55 disposed between each bearing 52 and a collar 53 provided on the shaft of each roller. The lower roller 31a and the upper roller 31b are respectively inserted into the block body 56 so as to be able to rotate freely, is the roller member 5 disposed in the upper part.
It comes into contact with a cam member 57 via 6a. The cam member 57 is of a type in which an inclined cam is formed on the circumference of the end of a cylindrical body, and when turned on by the spring clutch 59 or the solenoid 59s,
The rotational force of the drive gear 60 is transmitted to the shaft 6 via the spring clutch 59.
1, the cam member 57 is rotated, and the cam member 5
By making one full rotation, the upper roller 31b, lower roller 31a, spring 55...
- The cam member 5 is moved in the left and right directions A and B against
The center portion 57a of the inclined surface 7 is brought into contact with the roller member 56a, and the upper roller 31b and lower roller 31a are stopped at the center position of the left-right movement stroke, that is, the home position. Further, a gear 65 is fixedly installed on the lower roller 31a, and the electromagnetic clutch 65 is controlled by a signal from the control section C.
6 is turned on and the rotational force of the drive gear 67 is transmitted to the shaft 69 via the clutch 66 to rotate the transmission gear 70, thereby rotating the gear 65 meshing with the gear 70, thereby rotating the lower roller. 31a is rotated, and the sheet S, which had been stopped with its tip in contact with the contact portion between the upper roller 31b and the lower roller 31a, is now subjected to a conveying action.

Further, on the downstream side of the refeed roller pair 31, a light emitting section 71a in which a large number of light emitting elements are arranged in parallel and a large number of light receiving elements are arranged in proximity to the contact portion between the upper roller 31b and the lower roller 31a. An optical sensor 71 consisting of a light receiving section 71b
is arranged, and the lateral position of the sheet S is detected by the optical sensor 71.

Incidentally, on the upstream side of the pair of registration rollers 17, a resist portion optical sensor 75 having the same structure as the optical sensor 71 described above is arranged (see FIGS. 1 and 6). The lateral position of the sheet S sent to the pair of registration rollers 17 is detected.

Further, as shown in FIG. 1, a sheet guide 72 is disposed upstream of the refeeding roller pair 31, and the sheet S fed by the conveying roller pair 29 or the small size roller pair 30 is The sheet guide 72 guides the sheet to the contact portion between the upper roller 31b and the lower roller 31a of the refeeding roller pair 31. Note that, as shown in FIG. 4, the sheet guide 72 is fixed to a fixed block 73.73, and the upper roller 3 of the refeed roller pair 31
It is designed to move integrally with 1b.

On the other hand, on the upstream side of the refeed roller pair 31, as shown in FIGS. 1 and 4, the sheet S passes through the conveyance roller pair 29,
Alternatively, a refeed sheet detection sensor 74 is arranged to detect the passage of the small size conveyor roller pair 30, and the sensor 74 is equipped with a light detection element 74a and a detection arm 74b. When the leading edge of the sheet S is detected, it is detected that the rear end of the sheet S has passed the pair of conveying rollers 29 or the pair of small size conveying rollers 30 after a predetermined period of time from the detection. In other words, a stack of sheets stacked in a stepwise manner with their leading edges shifted one by one in the conveying direction is held between the pair of conveying rollers 29, or depending on the size, a pair of small-sized conveying rollers 30
When the sensor 74 detects the leading edge of the preceding sheet when it is being conveyed to the re-feeding roller pair 31 while being held between Since the sheet is conveyed a predetermined amount until it passes, the sheet is conveyed by the pair of conveying rollers 2 after a predetermined time required for conveying the predetermined amount from the detection of the leading edge of the sheet.
9 or the small size conveyance roller pair 30 is detected.

The control unit C also includes the above-mentioned re-feed sheet detection sensor 74.
Based on the detection, the driving sources of the conveying roller pair 29 and the small size conveying roller pair 30 and the driving source of the refeeding roller pair 31 are controlled, so that the preceding sheet is transferred to the conveying roller pair 29 or the small size conveying roller. A control means C1 is stored therein, which is programmed to stop driving the transport roller pair 29 and the small size transport roller pair 30 and start driving the refeed roller pair 31 when the transport roller pair 30 passes through the refeed roller pair 30. There is.

Since this embodiment has the above configuration, when multiplexing or double-sided copying is performed on one sheet, when the copying operation is started by pressing the copy button (not shown), the cassette 7
The sheet S supplied from a or 7b passes between the light emitting part 75a and the light receiving part 75b of the resist part optical sensor 75,
After being positioned in the sheet conveying direction by a pair of registration rollers 17 , the sheet is conveyed to the copying section 2 , where a toner image is transferred, and then further conveyed to the fixing device 20 via the conveying device 18 . At this time, the lateral position of the sheet S in the direction perpendicular to the conveyance direction is detected by the light receiving part 75b, which is light-shielded by the sheet S and the light-unshielded part, and an electric signal corresponding to the detected lateral position is detected. is output from the resist section optical sensor 75 and stored in the storage section of the control section C. Then, preparations are made in the control section C so that the pair of refeed rollers 31 can be moved in the axial direction in accordance with the detected lateral position.

Next, the sheet S that has undergone the fixing action in the fixing device 20 is conveyed to the sheet refeeding section 19 by the flapper 23 or the like to be subjected to multiple copying or double-sided copying. If it is detected that the direction length is shorter than the minimum length L min that can be transported by the sheet refeeding section 19 by the time it passes through the registration section optical sensor 75 or by the detection of the cassette size, the sheet S is discharged onto the tray regardless of the operator's designation of double-sided copying, etc.

A sheet S having a length L greater than the minimum length L min is conveyed by a pair of introduction conveying rollers 28 via a conveying path 27, and after a predetermined period of time after the leading edge of the sheet S reaches a pair of conveying rollers 29, the conveying roller By starting normal rotation of the pair 29, a loop is formed in the sheet S between the introduction conveyance roller pair 28 and the conveyance roller pair 29, and the skew of the sheet is corrected. Furthermore, when this sheet has the minimum length L win, the solenoid 4
5 is operated to pressurize the pair of small size conveying rollers 30.

Then, when the sheet S re-fed by the introduction conveyance roller pair 28, the conveyance roller pair 29, and the small size conveyance roller pair 30 is conveyed to the re-feed roller pair 31, the re-feed sheet detection sensor 74 is detected just before the refeed roller pair 31, and based on this, even after the leading edge of the sheet S contacts the contact portion between the stopped upper roller 31b and lower roller 31a, the transport roller pair 29 and the small size The conveying action of the sheet S by the forward rotation of the pair of conveying rollers 30 continues, and after the elapse of the predetermined time, both pairs of conveying rollers 29.3
The conveying operation of the sheet S is stopped, whereby an appropriate amount of flexure, that is, a loop is formed in the sheet S with the leading end of the sheet S in contact with the contact portion between the upper roller 31b and the lower roller 31a. Then, both conveyance roller pairs 29 and 30 rotate normally again,
When the electromagnetic clutch 66 is turned on at the same time, the drive gear 67
The rotation is transmitted to the gear 65 via the shaft 69 and the gear 70, the lower roller 31a starts rotating, and the sheet S is held between the rotating upper roller 31b and the lower roller 31a, forming the above-mentioned loop. Conveyance starts in this state. At the same time, five honey clutches are turned on, and the drive gear 60 is turned on.
rotation is transmitted to the cam member 57 via the shaft 61, and the rotation of the cam member 57 moves the block body 56 from its stop position, that is, the home position, in the direction B through the roller member 56a, and if necessary, moves the block body 56 to the rightmost end. F&A moved to
The sheet S is moved in the direction perpendicular to the direction of conveyance while being conveyed in such a manner that the sheet S is moved to the leftmost end in the direction B, and then moved again in the direction B from there. At this time, due to the existence of the loop described above, even if the rear end of the sheet is held between the conveyor rollers 29, the lateral movement of the sheet S will not exert any unreasonable force or deform the sheet S. It is done smoothly.

When the sheet S is moved in the lateral direction, the lateral position of the sheet S is checked by the optical sensor 71, and the lateral position of the sheet S is detected by the registration section optical sensor 75 and stored in the control section C. When the horizontal position of the sheet S coincides with the copying time, the spring clutch 59 is disconnected by a command from the control section C, and the horizontal movement of the upper roller 31b and the lower roller 31a is stopped.
After that, the upper roller 31b and the lower roller 31 continue for a predetermined period of time.
Due to the rotational conveyance action of a, the sheet S is conveyed from the sheet refeeding section 19 to the pair of registration rollers 17 with the lateral position corrected to be correct.

After conveying the sheet S, the electromagnetic clutch 66 is disengaged, and the rotation of each roller 3lb, 31a of the refeeding roller pair 31 is stopped.
2. It is returned to the central home position by the reset action of the optical sensor 63 and the like, and enters a standby state in order to correct the position of the next sheet S.

Next, the operation when double-sided copying or multiple copying is performed continuously on a plurality of sheets S will be described for sheets having lengths Ll and la in the conveying direction.

When the first original is set on the original table 4 and the desired number of copies N is specified, a copy button (not shown) is pressed to instruct the copying operation. The sheet S having a length Lma passes between the light emitting part 75a and the light receiving part 75b of the registration part photosensor 75 and has its lateral position measured, and then passes through the -th image forming process and is transferred to the pair of transport rollers 28. reach. At this time, if it is detected that the length of the sheet S in the conveyance direction is larger than LTa&M based on the time taken for the sheet S to pass through the registration optical sensor 75, the copying apparatus 1 does not accept continuous double-sided copying, etc., and the operator Issue a warning. When the sheet S reaches the introduction conveyance roller pair 28, the arm 28c is in a position where it has moved upward counterclockwise in FIG. When the sensor 32 detects the sheet S, the arm 28c moves downward clockwise as the sheet is fed by the introduction conveyance roller pair 28. After a predetermined time, that is, the leading edge of the sheet S moves to the upper and lower rollers 29b and 29a of the conveying roller pair 29.
After a loop is formed by contacting the contact portion between the sheets and the skew of the sheet is corrected, the pair of transport rollers 29 starts normal rotation according to a command from the control section C. At this time, small size conveyor roller pair 3
0 also rotates synchronously, but the upper roller 30b is in a retracted state and does not act on the sheet, and the trailing end of the sheet S is completely let out from the introduction conveyance roller pair 28 and reaches the swing area of the arm 28c. After feeding out the tall sheet S, the pair of conveying rollers 29 temporarily stops, and at the same time, the arm 28c moves upward in the counterclockwise direction.

Next, the conveying roller pair 29 is reversed this time so that L'<L
', the sheet S is returned to the upstream side by an amount L'2,
This allows the rear end of the sheet to enter the retraction section 50. Subsequently, when the second sheet S is conveyed after the first copying, the first sheet St is curled, and the trailing edge of the sheet does not completely enter the retraction section 50. If it does not exist, the situation will be as shown in FIG. 7(a). Even in this state, the second sheet enters the sheet detection sensor 3.
When detected by arm 2, arm 2 is detected as in the first case.
8c moves downward clockwise to press the rear end of the first sheet S1 against the lower guide plate 49 as shown in FIG. 7(b).

Therefore, the second sheet S2 is definitely the same as the first sheet S2.
S1, the sheet S1 is formed into a loop by the pair of transport rollers 29 as described above, and then sent along with the first sheet S1 to the L-straddling downstream side, and then reversed again by the transporting roller pair 29 to the L-straddling upstream side. (Figure 7 (C))
. This kind of action is repeated a set number of sheets N, and γ=L
When r - L 2, a bundle of N sheets stacked in a stepwise manner with one step or γ is formed.

At this point, the copying apparatus 1 is temporarily stopped, so the operator replaces the original on the original placing table 4, and then performs the second copying by pressing the button. Then, as shown in FIG. 8(a), the conveying roller pair 29 starts normal rotation and feeds the N sheets S, , as a bundle, until the leading edge of the -th sheet S1 is located downstream. After being detected by the refeed sheet detection sensor 74 of the feed roller pair 31 and fed a predetermined amount, that is, the rear end of the first sheet SI leaves the conveyance roller pair 29, and the second
The transport roller pair 29 is stopped before the th sheet S reaches the sensor 74.

Note that when conveying the sheets S as a bundle in this way, the upper roller 29b and lower roller 29a of the conveying roller pair 29 are connected by a gear train, so even if the conveying roller pair 29 repeats forward and reverse rotation, the sheets will continue to flow. The bundle Sn is conveyed without collapsing. Furthermore, at the time when the transport roller pair 29 stops as described above, the leading edge of the first sheet S1 is in contact between the rollers 31a and 31b of the refeed roller pair 31, as shown in FIG. 8(b). In this state, a loop is formed, and the other second and subsequent sheet bundles are held between the pair of conveying rollers 29.

Subsequently, while the transport roller pair 29 remains stopped, the refeed roller pair 31 rotates and feeds the first sheet while correcting the position in the lateral direction in the same way as when feeding one sheet. The SI is separated from other sheets and sent to the copying section 2 (FIG. 8(C)). At this time, unlike the other sheets, the trailing edge of the first sheet S1 has separated from the pair of transport rollers 29,
The sheet is sent separately from other sheets without being hindered by the pair of transport rollers 29. In addition, N-1 sheets are placed on the rear end of the first sheet whose position is corrected, but their weight is only a few logs at most, and the refeed roller pair 3
This does not impede the modification under 1. Subsequently, the second and subsequent sheets are repeatedly separated and conveyed in the same manner as described above, undergo double-sided copying, etc., and are discharged from the apparatus.

Furthermore, the length L m i in the transport direction. The operation when duplex copying is performed continuously on a sheet will be explained.

The sheet L sin, which has undergone the -th image forming process in the same way as the sheets S 2 and 8 described above, passes through the introduction conveyance roller pair 28, and then passes through the re-conveyance roller pair which is stopped as the arm 28c moves clockwise downward. 29.30, but when it is detected that this sheet S is the smallest sheet L m l n, the solenoid 45 operates to join both rollers 30a and 30b of the small size conveyance roller pair 30, and The transport roller pair 30 enters the operating state. After a predetermined period of time after the sheet detection sensor 32 detects the sheet S, that is, the leading edge of the sheet reaches the upper and lower rollers 29b, 2 of the conveying roller pair 29.
After a slight loop is formed by contacting the contact portion between the rollers 9a and the skewness of the sheet is corrected, the pair of conveying rollers 29 starts normal rotation according to a command from the control section C. Then, the conveyance amount Ll is such that the rear end of the sheet S is completely let out from the introduction conveyance roller pair 28 and comes to the downstream side of the swinging area of the arm 28c.
After feeding out the sheet S, the pair of conveying rollers 29 temporarily stops, and then reverses to return the weighed sheet S where L2<Ll to the upstream side, and then feed the second sheet Sa) The trailing end of the sheet is inserted into the retraction part 50 so that the rear end of the sheet does not enter the lower side of the first sheet S1. At this time, even if the rear end of the sheet S does not enter the retraction portion 50 due to curling or the like, the arm 28c
The second sheet S2 becomes the first sheet S2 due to the operation of
It will not go under the . Then, after a predetermined period of time has elapsed since the sheet detection sensor 32 detects the entry of the second sheet S2, the transport roller pair 29 rotates in both forward and reverse directions by the above-mentioned predetermined amount, so that the leading edge of the second sheet S2 reaches the transport roller pair. It stops when it moves from the contact part 29 to the above-mentioned position γ. Next, the conveyance roller pair 2 where the leading edge of the third sheet S2 has stopped
When reaching the contact part 9, the same operation as for the first sheet is performed, and this is repeated for the set number of sheets N, and the sheet refeeding unit 19 receives N sheets in a stair-like manner with each step being γ. A sheet bundle Sn is formed.

Then, when a second copying operation is performed after forming this sheet bundle Sn, the re-conveying roller pair 29, 30 starts normal rotation and N
The sheets Sn are fed as a bundle, and after the leading edge of the -th sheet S1 is detected by the downstream re-feeding sheet detection sensor 74 and fed by a predetermined amount, that is, the trailing edge of the first sheet S1 is The second sheet S moves away from the small size conveyance roller pair 30.
2 reaches the sensor 74, the re-conveying roller pair 29
．． 30 is stopped. In this state, the first sheet S,
is the roller 31a of the refeed roller pair 31.

A loop is formed with the leading end abutting between the sheets 31b, and the other second and subsequent sheet bundles are held between the pair of re-conveying rollers 29 and 30. Then, while the re-feeding roller pair 29 and 30 remain stopped, the re-feeding roller pair 31 rotates.
The first sheet S1 is separated from the others and sent to the copying section 2 while correcting the position in the lateral direction as in the case of feeding one sheet as described above. Subsequently, the second and subsequent sheets are conveyed separately from other sheets in the same manner as described above, undergo double-sided copying, etc., and are discharged from the apparatus.

(G) As described in detail of the invention, according to the present invention, when sheets stacked with their leading ends in the conveyance direction successively smoothed are held by the conveyance means and conveyed to the feed means, the preceding sheet is fed. When the sheet reaches the conveying means and separates from the conveying means, the driving of the conveying means is stopped and the driving of the feeding means is started to separate the sheet from other sheets and convey it. - The sheet can be reliably separated and re-fed without rubbing the image surface of the sheet on which an image has been formed and disturbing the image.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a copying apparatus according to an embodiment of the present invention;
FIG. 2 is a side view showing the arm, FIG. 3 is a perspective view of a pair of conveyance rollers and a pair of small size conveyance rollers, FIG. 4 is a perspective view of a pair of refeed rollers, FIG. 5 is a front view thereof, and FIG. The figure is a perspective view showing a resist portion optical sensor, and FIGS. 7 and 8 are explanatory diagrams of the operation of the copying apparatus. 74...Detection means (refeed sheet detection sensor), C1
... Control means S... Sheet So... Sheet group (bundle of sheets) Sl... Leading sheet

Claims (1)

[Scope of Claims] 1. A sheet conveying device in which sheets are separated and conveyed one by one from a group of superimposed sheets by sequentially shifting their leading ends in the conveying direction, comprising: a conveying means for pinching and conveying the group of sheets; , a feeding means that is located at a distance smaller than the length of the sheet in the conveying direction on the downstream side of the conveying means and that sequentially clamps and conveys preceding sheets of the sheet group; and the sheet group that is pinched and conveyed by the conveying means. a detection means for detecting passage of the preceding sheet by the conveyance means; and based on the detection by the detection means, when the preceding sheet passes through the conveyance means, the conveyance operation of the conveyance means is stopped and the conveyance operation of the conveyance means is stopped; A sheet conveyance device comprising: a control means for controlling the means to start a conveyance operation.