JP2846915B2 - Sheet transport device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus, and more particularly, to a mechanism for re-feeding a sheet from an intermediate tray in an image forming apparatus that forms images on both sides and in a multiplex manner.

(B) Conventional technology Conventionally, a double-sided image forming apparatus generally includes an intermediate tray for storing a sheet on which a first-side image has been formed, and sheets stacked in the intermediate tray after completion of image formation on the first side. Are separated from each other and sent out, and are conveyed again to the image forming section to form an image on the second surface. An important point in performing such double-sided image formation is the reliability of sheet conveyance as to whether the sheet can be properly conveyed. In particular, there is a problem in the reliability of the sheet re-feeding operation in which the sheets on which the first-side image has been formed are separated and fed one by one from the intermediate tray.

FIG. 15 shows an example of a conventional double-sided image forming apparatus. In the figure, 1 is an image forming apparatus main body, 2 is a document table on which a document is placed, 3 is a photosensitive drum for carrying a document image, A mirror 8 for forming an electrostatic latent image is an imaging lens.

Reference numeral 9 denotes a transfer electrode for transferring the toner image formed on the photosensitive drum 3 to the sheet P.

The sheet P accommodated in the cassette 10 is taken out by a paper feed roller 11, and the photosensitive drum 3 is moved by a registration roller 12.
After a toner image is formed on the first surface by the transfer electrode 9, the fixing device 13
As a result, the toner image is fixed. When an image is formed again on the same surface of the sheet P on which the image is formed on the first surface, the sheet P is guided to the transport path 15 by the switching guide 14,
It is stored in the intermediate tray 16. Also, the second side opposite to the first side
When an image is to be formed on the surface, the sheet P is guided to the transport path 17 by the switching guide 14, and after the sheet P is discharged halfway by the discharging roller 18, the discharging roller 18 is rotated in the reverse
As a result, the rear end of the sheet is guided to the conveyance path 20 and stored in the intermediate tray 16.

Each time one sheet of paper is placed in the intermediate tray 16, the whole bundle of sheets P placed on the intermediate tray is gradually fed to the transport roller pair.
The sheet P is conveyed at 21, and the sheets P are stacked in a stepwise manner with a slight shift for each sheet.

The sheet group stacked in this manner is conveyed collectively in the direction of the roller pair 22 after the image forming operation of the first surface is completed, and the lowermost sheet P leaves the roller pair 21 and simultaneously conveys the roller pair 21. By stopping, the roller pair 22
Only the lowermost sheet held in the
It is transported by 22 and the operation of the second surface is performed.
According to this conventional example, it is possible to improve double feed prevention performance at the time of re-feeding.

Incidentally, in order to form an image on both sides, a technique of stacking sheets P having a surface image formed on one side in a stepwise manner and refeeding the sheets is disclosed in JP-A-58-178373 and JP-B-63-18744. And so on.

However, in the above conventional example, only the lowermost sheet P to be re-fed is sandwiched by the roller pair 22 and separated from the roller pair 21, and a bundle of other sheets P is sandwiched only by the roller pair 21. Must be made. To do so, as shown in FIG.
It is necessary to set the distance between 21 and 22 to be slightly shorter than the length of the sheet P.

In this case, the toner and the like attached to the sheet P do not rub against each other, and the sheet P is not stained.
When feeding a sheet P of a plurality of sizes, that is, a sheet P longer than the distance between the roller pairs 21 and 21, the distance between the roller pairs 21 and 22 is shown in FIG. When the optimum roller pair position is satisfied as described above, the sheet P having a larger size is in a state as shown in FIG. 16 (b). That is, only the lowermost sheet P to be re-fed is separated from the roller pair 21 and the other sheets P are sandwiched by the roller pair 21, and two or more sheets P including the lowermost sheet P are sandwiched by the roller pair 22. Will be done. From this state, the rubber driving roller 22b feeds the lowest sheet. The other bundle of sheets P is not fed because it is nipped by the roller pair 21. Accordingly, FIG. 17, 18 as shown in FIG., The sheet P ₁ of the earliest moves in the arrow direction while rubbing the sheet P ₂ of handsome. Therefore, as at the time of multiple copy shown in FIG. 17, the toner of the upper surface handsome sheet P ₂ nip the lower surface to the sheet P ₁ in the range indicated by oblique lines in the figure attached, handsome sheet P Peel from ₂ . Also, when duplex copying,
18 As shown, the toner of the upper surface of the range indicated by oblique lines of the lowest sheet P ₁ together with the toner on the bottom surface of the nip portion of the sheet P ₂ of handsome adheres to peeling. There is a problem.

Therefore, in order to prevent the sheet P from being contaminated on the roller pair 22, the foremost sheet P is retracted to prevent the sheet P from being contaminated by rubbing, and as shown in FIG. A separation claw 23 and a branch path 24 are provided below the conveyance path 16 near the downstream side to separate the _first sheet P1 when the bundle of sheets P reverses. When the only P ₁ is sandwiched roller pair 22, roller pair 21 is proposed to be carried out only sheet P ₁ of the earliest and forward at the same time rollers 22 is stopped.

Challenge (c) to be Solved by the Invention However, even in advance by reducing the shape of the tip of the separation claw 23 for separating and subtle relationship between the sheet P ₁ in the tip and thin earliest separation claw 23 for separating there are liable sheet P ₁ is caught, it may cause a conveyance failure such as jamming. And
For example, when a jam generated between the roller pair 21 and the roller pair 22 is processed or the like, when a hand or finger is inserted on the transport path 16, there is a problem that the hand or finger is injured by the separation claw 23. .

Therefore, an object of the present invention is to provide a sheet conveying apparatus capable of improving operability in the case of jam processing or the like by retracting the separating unit from the sheet conveying path when a jam occurs and when the power is turned off. Is what you do.

(D) Means for Solving the Problems According to the present invention, there is provided a sheet carrying means for carrying in a sheet, the carried sheet is transported by a predetermined amount in the forward and reverse directions, and is stacked while being shifted by a predetermined amount and loaded. A sheet conveying unit that conveys a bundle of sheets, a sheet discharging unit that discharges an earliest sheet of the conveyed sheet bundle, and a sheet conveying unit that is located between the sheet discharging unit and the sheet conveying unit; A separation transport path for retreating a part of the bundle and a first position for separating one of the separated sheets of the sheet bundle and retreating to the retreat transport path, and a second position where the sheet is not separated can be selected. Means for separating the foremost sheet by the separating means placed at the first position while the sheet bundle is being conveyed, and retreating one of the separated sheets to the retreat conveyance path. To take out a sheet of In a sheet transporting apparatus having a sheet transporting unit, a sheet unloading unit, and a control unit for controlling a separating unit, when a paper jam occurs, the control unit controls the separating unit to select a second position. It is characterized by being added to the means.

When a paper jam occurs in the vicinity of the separation unit, a control function of driving the sheet conveyance unit and the sheet unloading unit for a predetermined time to pull out the sheet bundle being conveyed from the retreat conveyance path is added to the control unit. It is characterized by having done.

Further, a control function for controlling the separation means to select the second position when the power is turned off is added to the control means.

(E) Operation Based on the above configuration, the sheet is carried in by the sheet carry-in means, the carried-in sheet is carried by the sheet carry means in the forward and reverse directions by a predetermined amount, and the sheets are stacked by being shifted by a predetermined amount, and the sheet bundle is stacked. After the formation, the control unit controls the sheet conveying unit, the sheet unloading unit, and the separating unit to separate the foremost sheet by the separating unit located at the first position during the conveyance of the sheet bundle. After retreating one of the sheets to the retreat conveyance path, the first sheet is carried out. On this occasion,
When a paper jam occurs, the separation means is controlled by the control means to the second position.
Position.

Further, when a paper jam occurs, the sheet conveying means and the sheet discharging means controlled by the control means pull out the sheet bundle being conveyed from the retreat conveyance path.

Further, when the power is turned off, the separating unit is located at the second position.

(F) Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows an image forming apparatus to which the present invention is applied, and shows a copying apparatus that performs double-sided and multiple copies using different colors.

In FIG. 1, the same configuration as the conventional example shown in FIG.
The same reference numerals are given to the members that operate, and the description is omitted.

Therefore, a portion from the conveying path 23 where the conveying paths 15 and 20 join to the registration roller 12 will be described with reference to FIG. 1 and FIG.

A sensor 24 for detecting the leading end of the sheet P is provided at a downstream end of the conveying path 23, and a conveying roller pair 25 is provided slightly upstream of the sensor 24. Also, the upper guide of the transport path 23
The lower guide 27 extends diagonally downward, and a substantially horizontal lower guide 27 is provided below the upper guide 26 so as to face the lower guide 27. A drive roller 28a is provided, and a resin driven roller 28b having a small coefficient of friction is provided so as to be able to move up and down opposite the drive roller 28a, and is urged downward by a leaf spring 29.

An upper guide 30 and a lower guide 31 similar to the upper and lower guides 26 and 27 are provided on the right side of the roller pair 28a and 28b.
A pair of rollers 32a and 32b having a nip portion are provided on the right side of the lower guide 31 on the right side of the lower and upper guides 31, 31. The roller 32a is supported by a fixed shaft, and the roller 32b is vertically movable. It is urged downward by a spring 34 so as to press against the roller 32a. Upper and lower guides 35, 36 curved upward from a flat surface to the right of the pair of rollers 32a, 32b
6 is provided such that the upper surface thereof is substantially flush with the nip portion of the roller pair 32a, 32b.

A sensor 33 for detecting the sheet P is attached to the lower guide 31.

Then, the end of the lower guide 31 on the roller pair 28a, 28b side is bent to form a retreat path 37, and the retreat path 37 and the roller 28
A separation claw 38 which is supported by a shaft 38a and is driven by a solenoid 39 is provided between the separation claw 38a. As shown in FIG. 3, the separation claw 38 slightly protrudes from the lower guide 31 to separate the _first sheet P1 of the bundle of sheets P from a first position indicated by a solid line.
A second position indicated by a dashed line retracted below the surface of 31 is taken.

As shown in FIG. 4, the upper guide 30 can be opened and closed about a shaft 30a. When the upper guide 30 is closed, the rollers 28b and 32b are connected to the rollers 28a and 32a supported by the lower guide 31. It is urged by the leaf springs 29 and 34 so as to be pressed against each other. The rollers 28b and 32b are supported at the ends of the leaf springs 29 and 34, respectively.

The driving rollers of the roller pair 25, the rollers 28a and 32a are connected to the stepping motors 25m, 28m and 32m, respectively, by a gear train or the like.
The 28 m and 32 m signal circuits are connected to the control unit 40, and are capable of normal / reverse rotation and rotation at a predetermined angle.

Further, signal circuits of the sensors 24 and 33 and the solenoid 39 are connected to the control unit 40.

The rollers 28a and 32a are made of rubber or the like having a large friction coefficient, and the rollers 28b and 32b are made of resin or the like having a small friction coefficient.

Reference numeral 41 denotes a keyboard for instructing the number of copies, double-sided mode, copy start, and the like. Reference numeral 42 denotes a size detection device, and each signal circuit is connected to the control unit 40.

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

First, the operation of storing a bundle of a plurality of sheets P in the lower guide 27 (refeeding path) will be described with reference to the flowchart of FIG.

When a double-sided or multiple copy mode is set by the keyboard 41 and a copy start is instructed, the earliest sheet P on which an image has been formed on one side by the photosensitive drum 3 is taken out of the cassette 10 as described above. It is sent to the roller 25 that has started to rotate. Step S2 in FIG.
After the sensor 24 detects the leading edge of the sheet P _1, the leading edge of the sheet reaches the nip of the rollers 28 a and 28 b to form a loop, and after a lapse of a predetermined time t ₁ required to align the leading edges (step S 3), Start the motor 28m (Step S
Four). Then, the rear end of the sheet is set with the roller pair 25 and
Rotating the sheet P ₁ is roller pair 28a, a predetermined time required for a predetermined distance transport has been set in advance from being sandwiched 28b t ₂ only motor 28 in order to pull out from (Step S5, the sixth
Figure), reversed the t ₂ elapsed after the motor 28 m (step S6), t
A short predetermined time t ₂ -.DELTA.t than ₂ to stop the motor 28m after reversed (step S7 and S8). Sheet P ₁ by the reverse rotation of the motor 28m is conveying roller pair 28a, by 28b in the opposite direction, the leading end of the sheet P is roller pair 28a, from the nip portion of 28b by a predetermined distance l is located downstream (Figure 7). Sheet
The rear end of the P ₁ is guided on the guide 27 enters the lower roller pair 25.

The rotation of the roller pair can be controlled by the number of pulses sent from the control unit 40 to the motor 28m. That is, after the leading end of the sheet reaches the nip of the pair of rollers 28a and 28b, the number of pulses corresponding to the rotation angle of the motor 28m required to convey the sheet P by a predetermined distance is sent, thereby making the pair of rollers 28a and 28a,
28b can be controlled.

Next, in step S9, it is determined whether or not the stacking of the set number has been completed, and if not, the process returns to step S2. Then, the next sheet P is conveyed, and the roller pair 28a, 28b
, The pair of rollers 28a and 28b operate exactly the same as the previous _one while holding the _first sheet P1, and the second sheet P
Is located downstream of the nip portion of the rollers 28a and 28b by l. At this time, the sheet P of the first sheet is conveyed along the sheet P ₂ of the second sheet, the leading edge of the sheet P ₁ in the earliest 2
It is located further downstream by 1 from the leading end of the _second sheet P2.

Thus the two sheets P ₂ are overlapped in a state deviated by l. By performing this operation on the set number of sheets P, the sheets can be sequentially stacked while being shifted by 1 as shown in FIG. Then, the motor 25m stops (step S10).

In these processes, the sheet P is applied to the roller pairs 28a and 28b.
When the sheet P is abutted, the protruding resin roller 28b having good slippage protrudes into the conveyance path, so that the leading end of the sheet P can smoothly enter the nip of the roller pair 28a, 28b.

Next, the stacked sheets P are printed on both sides or multiple copies.
The operation of re-feeding the paper for the second image formation will be described with reference to the flowchart shown in FIG.

When a start is instructed by the keyboard 41 (step S11), rotation of the motors 28m and 32m starts, and the stacked sheets P are sent to the pair of rollers 32a and 32b (steps S12 and S1).
3). When the trailing edge of the foremost sheet P ₁ is passed through the tip of the separation claw 38, to turn on the solenoid 39 to drive the separation pawl 38, by moving the separation pawl 38 in a first position at the same time (the state 10
Reverse the motors 28m and 32m (shown in the figure) (Step S16,1
7). This timing is determined by the sensor 33 as the first sheet P ₁
Elapsed time t ₃ since the tip of is detected (step S14)
(Step S15). At this time, as shown in FIG. 10, the rear end of the _second sheet P2 is
Located on top.

Then, the motor 28 m, by the reverse rotation of 32m, the sheet P ₁ in the least significant (earliest) is its rear end is separated into the separation claw 38 retreats to the retreat path 37. Other sheets P are bundled with roller pairs 28a, 28b,
The lower guides 27 and 31 (conveyance paths) are moved in the opposite directions by 32a and 32b.

Then, only the sheet P ₁ in the earliest the roller pair 32a, (see FIG. 11) when it is clamped by 32b at the same time the motor 32m when the motor 28m is stopped and reversed (forward) (Step S1
7,18,19,20), at the time when the first sheet P reaches the registration roller 12 and forms a loop t ₅ hours, the motor 32m
Stops, and the solenoid 39 is turned off (steps S21 and S2).
2). Incidentally, t _3, S18 of t ₄ h in step S15, step S2
1 t ₅ hours is set by the control unit 40 in accordance with the information of the sensor 33 and the size detection device 42.

The roller pairs 32a, when the sheet P ₁ of the earliest is conveyed by 32b, the other sheets P are rollers 28a, 28b
, So that only the _first sheet P1 is reliably separated and conveyed out, and is not stained.

If the set number of sheets has not been completed, the process returns to step S12, and the same operation is repeated. However, when the copying of the set number of sheets is completed (step S23), the operation is completed.

In the above embodiment, it has dealt with the case where the lowermost sheet P and the sheet P ₁ in the earliest on the lower guide 27 (intermediate tray) is unloaded from the sheet P ₁ in the earliest (refeed) 7 is conveyed to -l, that is, to the left of the pair of rollers 28a and 28b. For this purpose, as shown in FIG. 12, since the sheet P cannot be conveyed leftward and leftward by the pair of rollers 28a and 28b, a conveying roller 43 capable of conveying the sheet P is provided. Also, the uppermost sheet P becomes the _first sheet P1, and the separation claw is formed.
38 is provided between the upper guide 30 and the roller 28b.
The bent portion 30a of the upper guide 30 forms a retreat path.

 It can be configured in this way, and the effect is the same.

 Next, an operation when a jam occurs will be described.

When a jam occurs near the separation portion, it is difficult to detect the jam at the same time, so a case where a jam occurs between the roller pair 28a, 28b and the roller pair 32a, 32b by a known jam detecting unit will be described. .

When a jam is detected by a jam detecting unit that determines that a jam has occurred unless the _first sheet P1 is detected within a predetermined time by a sensor (not shown), the solenoid 39 that drives the separation claw 38 is turned off, and the separation is performed. The pawl 38 moves to the second position and is retracted from the upper surface of the lower guide 31.

At the same time, the roller pairs 28a, 28b, 32a, 32 b is stopped after a predetermined amount forward, pulling the sheet P ₁ in the earliest from the retraction path 37.

Therefore, when the operator clears the jam, the separation claw 38 is retracted, so that the operator does not hurt his hand or finger.
Since the sheet P ₁ is withdrawn from the withdrawal line 37 can be facilitated by the jam.

Furthermore, even when the power is cut off during operation due to a power failure or the like, the separation claw 38 takes the second position, so that the sheet P can be processed safely.

Incidentally, FIG. 13, to separate the sheet P ₁ in the earliest as shown in FIG. 14, also in the mechanism for retracting the other sheets P in the bundle of sheets P, the present invention to retract the separation pawl when a jam occurs Can be applied.

In this embodiment, the bundle of sheets P is not separated at the time of reverse feeding, but is separated and retracted while being conveyed in the unloading direction. That is, each sheet P is the first sheet
Separating claw 45 when the bundle of rollers 28a of the stacked sheets P from P ₁ are offset the same amount at a time, the leading end of the sheet P ₁ in the earliest during unloading by 28b arrives below the separation claw 45 is axial 45a comes into contact with the sheet P earliest as shown in FIG. 14 by a solenoid or the like (not shown) around a, retracts the bundle of remaining sheets P to the branch passage 44, the leading end of the sheet P ₁ in the earliest the roller Vs 32
a, after being sandwiched 32b, further, when the trailing end of the sheet P ₁ of the earliest is released roller pair 28a, the holding of 28b, rollers 28a, 28b is reversed, except earliest sheet P ₁ Then, the roller pair 28a, 28b stops. The pair of rollers 32a and 32b stops when the _first sheet P1 is sent to the registration roller to form a loop.

Earliest sheet P ₁ by nuclear is unloaded without sliding contact with the other sheet P, can prevent contamination of the sheet P,
Further, as described above, when the sheet P is jammed, it is apparent that the same action as in the present invention can be performed.

(G) Effects of the Invention As described above, according to the present invention, if a jam occurs during re-feeding of a sheet, the separation claw retreats to the second position, so that the operator can remove his or her hand when clearing the jam. Jam processing can be performed without damaging the finger, thereby facilitating the jam processing operation.

In addition, when a jam occurs, the sheet conveying unit and the sheet unloading unit pull out the sheet from the retreat conveying path, thereby further facilitating the jam clearing operation.

Further, when the power is turned off due to a power failure during operation or the like, the sheet is easily processed by retracting the separation claw to the second position.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of a copying machine in which a sheet conveying device of the present invention is implemented, FIG. 2 is a longitudinal sectional front view of the sheet conveying device,
FIG. 3 is an enlarged front view of the separation claw, FIG. 4 is a perspective view showing an openable and closable structure of a refeeding conveyance path, FIG. 5 is a flowchart of sheet stacking, and FIGS. FIG. 8 is a longitudinal front view showing the state of the intermediate stage, FIG. 9 is a flowchart for carrying out the sheet, FIG. 10 is a longitudinal front view showing the state immediately after the rear end of the first sheet has passed the separation claw, FIG. 11 is a longitudinal sectional front view showing a state where the leading end of the earliest sheet is sandwiched by sheet discharging means, FIG. 12 is a longitudinal sectional front view showing another embodiment, FIG. 13 and FIG. Longitudinal sectional front view of the embodiment,
FIG. 15 is a longitudinal front view of a conventional example, FIG. 16 (a) is a front view showing a correct arrangement of the conveying rollers for a short sheet, and FIG. 16 (b) shows a state in which a long sheet is carried out with the same roller arrangement. FIG. 17 is a front view showing a state in which the sheet is soiled, and FIG. 19 is a front view showing a conventional proposal example. 25 …… Sheet carrying means (transport roller pair), 28a, 28b ……
Sheet conveying means (drive roller, driven roller), 32a, 32b
…… Sheet unloading means (roller pair), 37… Escape transport path (Escape path), 38… Separation means (separation claw), 40… Control means (control unit), P… Sheet, P ₁ … The first sheet.

Claims (3)

(57) [Claims] 1. A sheet carrying means for carrying a sheet, and a sheet carrying means for carrying the carried sheet in a forward / reverse direction by a predetermined amount, shifting the sheet by a predetermined amount, and carrying a bundle of the stacked sheets. Sheet ejection means for ejecting the earliest sheet of the conveyed sheet bundle, and retreat conveyance positioned between the sheet ejection means and the sheet conveyance means for retreating a part of the sheet bundle. Path, a separation unit capable of selecting a first position at which one of the sheets separated by separating a part of the sheet bundle and retreating one of the separated sheets to the evacuation conveyance path, and a second position at which the sheet bundle is not separated, and conveying the sheet bundle The first sheet is separated by separating means placed at the first position, and one of the separated sheets is retracted to the retreat conveyance path, and then the sheet is discharged so as to carry out the first sheet. Conveyance means, sheet unloading A sheet conveying device having a control unit for controlling a step and a separation unit, wherein a function of controlling the separation unit to select a second position when a paper jam occurs is added to the control unit. Sheet conveying device. 2. A control function for driving a sheet conveying means and a sheet discharging means for a predetermined time in order to pull out a sheet bundle being conveyed from the retreat conveying path when a paper jam occurs near the separating means. Claim 1 added to the means
The sheet conveying device as described in the above. 3. The sheet conveying apparatus according to claim 1, wherein a control function for controlling the separation unit to select the second position when the power is turned off is added to the control unit.