JP2001039563A - Paper feeding device and picture image formation device furnished with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly return another sheet to a specified loading position without lowering throughput and without influencing upon sheet carrier precision in a simple structure. SOLUTION: Sheets P loaded on sheet loading parts 11, 19 are delivered by a feeding means 10, and the sheets; P are separated one by one by a separation means 13. Additionally, a rotor 17 to make contact with a sheet P1 instead of the feeding means 10 at a position corresponding to a cutout part 10b of the feeding means 10 is provided coaxially with the feeding means 10 free to rotate, and it is constituted so as to form a clearance G between the rotor 17 and the separation means 13 at the time when the rotor 17 makes contact with the sheet P1. Thereafter, a returning means 18 is made to appear in the clearance G so as not to enter a carrier locus of the sheet P1 when this clearance G is formed, and the other sheet P entering this clearance G with the delivered sheet P1 is pushed back to the sheet loading parts 11, 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeder and an image forming apparatus having the same, and more particularly, to a sheet feeder having a sheet stacking portion which is stacked in an inclined state and provided with separating means for separating the sheet.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, and a facsimile, an image is formed on sheets such as plain paper, cardboard such as postcards and envelopes, and special sheets such as plastic thin plates. Although such sheets are supplied to the image forming unit, such sheets are supplied manually one by one, or automatically and continuously by a sheet feeding device.

[0003] Such a paper feeder is provided with a separation unit for separating sheets one by one, and as a configuration of this separation unit, a nail separation system and a pad separation system are generally known. I have.

Here, the claw separation method locks the corner of the leading end of the laminated sheet with the separation claw, as is well known, and
By rotating the paper feed roller disposed on the upstream side of the separation claw in the paper feeding direction, the uppermost sheet is bent between the paper feed roller and the separation claw, and this bending reaches the limit and is repelled. Is used to separate the top sheet from the next sheet and feed only the top sheet. Note that this claw separation method is the simplest separation mechanism, and is often used in copiers and printers of low-cost equipment. However, since it utilizes the deformation resistance of the sheet, it is affected by the rigidity and humidity of the sheet. And the frequency of double feed and non-feed is relatively high.

On the other hand, in the pad separation system, as is well known, the friction coefficient between the paper feed roller and the sheet is μ1, the friction coefficient between the separation pad and the sheet is μ2, and the friction coefficient between the sheets is μ3. In this case, the paper feed roller and the separation pad are configured so that the relationship of μ1>μ2> μ3 is satisfied, and the sheet is sandwiched between the rotating paper feed roller and the separation pad pressed against the paper feed roller. In this method, the top sheet and the next sheet are separated, and only the top sheet is fed.

In this pad separation system,
If a rubber material is selected in consideration of the frictional force between the sheet feeding roller and the sheet, the frictional force between the sheet and the sheet, and the frictional force and the wear characteristics between the sheet and the separation pad, a highly reliable separation mechanism can be configured.

FIG. 14 is a diagram showing a configuration of a sheet feeding apparatus using such a pad separation system.
Reference numeral 00 denotes a paper feeding device, and 110 denotes a substantially D-shaped paper feeding roller when viewed from the side. The paper feeding roller 110 has an arc portion 110a and a linear portion 110b. 111 is a pressure plate,
A plurality of sheets P are set on the pressure plate 111 in an inclined state, and the pressure plate 111 is
The upper sheet P is urged toward the paper feed roller 110.

Reference numeral 113 denotes a separation pad for separating the sheet P, which is mounted on the holder 114. Here, the holder 114 is rotatably supported by a paper feeding device main body (not shown) by a shaft 114 a and is urged by a predetermined force F toward the paper feeding roller 110 by a pad spring 115.

Reference numeral 117 denotes an idle roller, which is rotatably mounted on the side of the feed roller 110 with respect to the feed roller shaft 110c. Here, the idle roller 117 is connected to the circular arc portion 11 of the sheet feeding roller 110.
0a, the arc portion 110a of the paper feed roller 110 does not come into contact with the separation pad 113, that is, the linear portion 110b of the paper feed roller 110 faces the separation pad 113. When the separation pad 1
13.

Reference numeral 116 denotes a cam.
6, the sheet supply roller 110 and the pressure plate 111 are maintained in a separated (released) state before the start of sheet supply.

Next, the paper feeder 10 constructed as described above
The paper feeding operation of 0 will be described.

Before the start of sheet feeding, the sheet feeding roller 110 and the pressure plate 111 are separated (released) by the cam 116. When the sheet feeding operation is started, first, the sheet feeding roller 110 is released.
Rotates in the direction of the arrow in FIG.
0 rotates in a direction to release the separation between the sheet feeding roller 110 and the pressure plate 111, whereby the pressure plate 111 feeds the sheet P by the spring 112 using a shaft (not shown) as a fulcrum. It rotates in the direction of pressing against the roller 110.

Thereafter, the arc portion 110 of the paper feed roller 110
a comes into contact with the uppermost sheet P1, and the uppermost sheet P1 is sent out toward the separation pad 113. At this time, the next sheet P2 is attracted to the uppermost sheet P1 by the action of static electricity, or
When the frictional force acts between the first sheet P2 and the next sheet P2, the next sheet P2 may be sent together with the top sheet P1.

However, the next sheet P2 is separated from the uppermost sheet P1 by the separation pad 113 in the following manner.
And only the uppermost sheet P1 is fed. That is, when the leading edge of the next sheet P2 abuts against the separation pad 113, the movement of the next sheet P2 is hindered, and the next sheet P2 is temporarily separated from the uppermost sheet P1.

The arc portion 110a of the paper feed roller 110
The frictional force between the uppermost sheet P1 and the next sheet P2 is f1, the frictional force between the next sheet P2 and the separation pad 13 is f2, and the frictional force between the uppermost sheet P1 and the next sheet P2. To f
Assuming that the sheet feed roller 110 and the separation pad 113 are configured such that the relationship of f1>f2> f3 is established, as the sheet feed roller 110 rotates, the uppermost sheet P1 and the next sheet P2 become Are both paper feed rollers 110
When the state is sandwiched between the arc portion 110a and the separation pad 113, the movement of the next sheet P2 is hindered by the frictional force f2 between the separation sheet 113 and the next sheet P2. Top sheet P1 separated from P1
Only will be fed.

In this manner, the uppermost sheet P1
When feeding the paper, the separation pad 113 is
Is pressed down by contact with the circular arc portion 110a. At this time, since the diameter of the idle roller 117 is formed to be slightly smaller than the diameter of the arc portion 110a of the paper feed roller 110, the idle roller 117 is separated from the separation pad 113.

When the separation of the sheet P1 is completed in this way, the cam 116 returns to the position where the pressure plate 111 is pushed down, whereby the sheet feeding roller 110 and the pressure plate 1 are again returned.
11 is separated (released). Thereafter, the sheet feeding roller 110 returns to the same position as before the start of sheet feeding, and the sheet feeding operation is completed.

When the sheet feeding device 100 is attached to a printer (not shown), the sheet P1 separated in this way is transported by a transport roller 102 of the printer.
After being conveyed while being pinched by the pinch roller 103, the image is printed by the printing unit 104 of the printer.

Here, when the conveyance of the sheet P1 by the conveyance roller 102 and the pinch roller 103 is started, the sheet P1 is usually not completely removed from the sheet feeding device 100. In the process, the next sheet P2 once separated by the separation pad 113 is attracted to the sheet P1 by the action of static electricity, or is likely to be sent together with the sheet P1 by frictional force with the sheet P1. is there.

However, at this time, since the idle roller 117 comes into contact with the separation pad 113 as shown in the figure, the next sheet P2 is prevented from being fed. In addition, regarding the sheet P1, the sheet P1 is in a state of receiving the load by the pressing portion until the rear end of the sheet P1 passes through the pressing portion between the separation pad 113 and the idle roller 117. In the state of being pulled, that is, under the back tension,
The sheet is conveyed by the conveying roller 102 and the pinch roller 103.

The paper feeder 1 is operated by the load.
The sheet P can be held by tilting the sheet P. However, the sheet P slides down due to the weight of the sheet P while repeating such a sheet feeding operation, or the next sheet P2 or further. The next sheet or the like causes a so-called avalanche phenomenon, and the sheet feeding roller 110 and the separation pad 1
13, it is easy to fall into the press contact portion. In particular, sheet P
Is slippery, such as an OHP sheet,
Since the sheet P easily slides down due to its own weight, the sheet P causes an avalanche phenomenon, so that it becomes extremely easy to fall into the pressure contact portion between the sheet feeding roller 110 and the separation pad 113.

Therefore, as a countermeasure against this, conventionally, a return lever 118 is provided, and after the rear end of the sheet P passes through the pressure contact portion, for example, when the printing operation is completed, the sheet dropped into the pressure contact portion by the return lever 118 is returned. P is returned to a predetermined loading position.

The return lever 118 waits at a position to close the sheet P conveyance path before the start of sheet feeding. However, when the sheet feeding operation is started, the return lever 118 is retracted from the sheet P conveyance path to separate and feed the sheet P. Move to a position where it does not interfere with the paper.

After the rear end of the sheet P1 has passed through the pressure contact portion, the sheet P1 pivots and moves to the position shown in the figure, thereby moving the next sheet P2 or the next sheet or the like to a predetermined position. Return to loading position. Here, the return lever 118
Is performed using the reverse rotation of the paper feed roller 110 (rotation opposite to the paper feed direction) as shown in FIG.

When the paper feed roller 110 rotates in the reverse direction, the cam 116 that has separated the pressure plate 111 from the paper feed roller 110 operates in the reverse direction to act on the pressure plate 111, and the pressure plate 111 moves in the direction of the paper feed roller 110. Become biased. In order to prevent this, a lock lever 119 as shown in FIG. 14 is provided.

[0026]

However, in such a conventional sheet feeding apparatus, the operation trajectory for the sheet returning operation of the return lever 118 takes the form of entering the conveyance trajectory of the sheet P. If the sheet P1 is returned while the sheet P1 is pressed between the idle roller 117 and the separation pad 113, the sheet being conveyed or the next sheet may be damaged by the return lever 118.

Therefore, in order to prevent this, the sheet must be returned after the printing operation on the sheet is completed or after the sheet is completely discharged out of the recording apparatus. However, in such a configuration, extra printing time is required due to the return operation, especially when printing a plurality of sheets.
Throughput decreases.

On the other hand, the operation of the return lever is performed by the reverse rotation operation of the paper feed roller 110 as described above,
Since the drive transmission switching mechanism to the sheet feeding device and the operation sequence are complicated, the cost of the entire recording apparatus has been increased.

Further, in order to prevent the sheet P from dropping, even during printing, the rear end of the sheet P is pressed by the idle roller 117 and the separation pad 113, so that a load (back tension) is always applied during printing on the sheet P. This affects the conveyance accuracy of the sheet P.

Accordingly, the present invention has been made in view of the above situation, and has a simple structure, and can reliably determine the position of another sheet without lowering the throughput and without affecting the sheet conveyance accuracy. It is an object of the present invention to provide a paper feeder capable of returning to the stacking position and an image forming apparatus having the same.

[0031]

According to the present invention, there is provided a sheet feeding apparatus for separating and feeding sheets stacked one by one in a state where the sheets stacked on the sheet stacking section are inclined, wherein the sheets stacked on the sheet stacking section are fed. A feeding unit having a cutout formed on the outer peripheral surface that comes into contact with the sheet, and a position corresponding to the cutout of the feeding unit that is provided rotatably coaxially with the feeding unit. In place of the feeding means, the rotating body that comes into contact with the sheet, and the sheet that is sent out by the feeding means abuts and separates the sheets one by one while the rotating body comes into contact with the sheet. A separating unit configured to form a gap between the rotating body and another separating unit that appears in the gap when a gap is formed between the separating unit and the rotating body and that enters the gap. Push the sheet back to the sheet stacking section And means to, the said return means is characterized in that appearing in the gap in a range that does not enter the transport path of the sheet to be conveyed.

Further, the present invention is characterized in that the diameter of the rotating body is made smaller than the diameter of the feeding means so as to form the gap.

Further, the present invention is characterized in that the separating means is configured to be in pressure contact with the outer peripheral surface of the feeding means, but not to contact the rotating body.

In the present invention, the return means may be a return lever which appears in the gap in conjunction with a sheet feeding operation of the feed means and moves in a direction for returning the sheet to the sheet stacking portion. It is a feature.

Further, the present invention is characterized in that the return lever also serves as means for preventing sheets stacked in the sheet stacking section from being inclined in the gap.

Further, according to the present invention, the return means is provided on a belt which circulates at a constant period in conjunction with a sheet feeding operation of the feeding means and appears in the gap, and the sheet is placed on a sheet stacking portion. The thin plate moves in the returning direction.

Further, the present invention is characterized in that the thin plate has flexibility so as to bend while being in contact with the outer peripheral surface of the feeding means before the gap is formed.

Further, the present invention is characterized in that there is provided means for preventing sheets stacked in the sheet stacking section in an inclined state from falling into the gap.

In the present invention, the operation of separating and feeding the sheets one by one is completed by one rotation operation of the feeding means in one direction, and the operation of returning the other sheets to the sheet stacking unit. Is performed at a specific timing during one rotation of the feeding means.

[0040]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a side sectional view of a main part of an ink jet recording apparatus which is an example of an image forming apparatus provided with a sheet feeding device according to the first embodiment of the present invention. Note that this ink jet recording apparatus is integrally provided with a paper feeder.

In FIG. 1, reference numeral 1 denotes a paper feeder provided with a sheet storage section 1A. The paper feeder 1 has a recording device main body having a predetermined angle (30 ° to 60 °) as shown in FIG. The sheet P, which is attached to the sheet storage unit 50 and is provided in the sheet storage unit 1A and constitutes a sheet stacking unit for stacking the sheets P in an inclined state, and the sheet P supported by the pressure plate 11 is supplied in a substantially D-shape in side view. Paper feed roller 1 as a feeding means
0, paper is fed in a substantially horizontal direction toward a printing unit 4 which is an image forming unit provided in an ink jet recording apparatus main body (hereinafter, referred to as a recording apparatus main body) 50.

By mounting the sheet feeding device 1 at an angle with respect to the horizontal in this way, the installation area of the sheet feeding device 1 and the recording apparatus main body 50 can be reduced. Reference numerals 2 and 3 denote a transport roller and a pinch roller provided on the recording apparatus main body 50, respectively.

On the other hand, the paper feed roller 10 is
And a substantially linear portion 10b formed of two straight lines and a circular arc portion, which are cutout portions formed on the outer peripheral surface of the sheet P, which is driven by a driving unit (not shown) provided at the sheet P. And an arcuate portion 10a in contact therewith,
In the case of the present embodiment, the sheet feeding operation is completed when the sheet feeding roller 10 makes one rotation.

The circular arc portion 10a of the paper feed roller 10
Is set to be longer than the distance from the sheet stacking surface 19 to the transport roller 2, so that even if a slight slip occurs between the sheet feeding roller 10 and the sheet P, The configuration is such that the paper is not defective.
Further, the arc portion 10a is formed of a rubber-like member such as rubber or an elastomer having a high friction coefficient.

The pressure plate 11 is rotatably mounted on a rotation shaft 11a provided in the sheet storage section 1A, and is urged toward the paper feed roller 10 by a spring 12, whereby the pressure plate 11 is placed on the pressure plate. The sheets P set in a stacked state are urged toward the paper feed roller 10. Reference numeral 16 denotes a sheet feeding roller 1 in a series of sheet feeding operations.
0 is a cam that rotates in conjunction with the rotation of 0.
Thus, the pressure plate 11 can be switched between approaching and separating from the paper feeding roller 10 during the paper feeding operation of one rotation of the paper feeding roller 10.

In the same figure, reference numeral 13 denotes a separation pad as separation means for separating the sheet P, which is mounted on the holder 14. Here, this holder 14
Is rotatably supported by a shaft 14a provided in the sheet storage section 1A, and is urged by a pad spring 15 toward the paper feed roller 10 with a predetermined force F.

Reference numeral 17 denotes an idle roller, which is a rotating body.
It is attached rotatably with respect to 0c. here,
The idle roller 17 has a diameter that is slightly smaller than the diameter of the paper feed roller 10, and
0a and the separation pad 13 do not come into contact, that is, when the substantially linear portion 10b of the paper feed roller 10 is opposed to the separation pad 13, as shown in FIG. While rotating.

In this embodiment, the holder 14 on which the separation pad 13 is mounted is restricted from rising by a restriction portion (not shown), whereby the separation pad 13 is pressed against the paper feed roller 10. However, as shown in the drawing, the idle roller 17 is kept at a fixed distance and does not come into contact with the idle roller 17.

On the other hand, in the figure, reference numeral 18 denotes an example of a return means, which is a return lever having a locking portion 18a provided at the tip thereof. The return lever 18 rotates during a series of sheet feeding operations. When the sheet feeding operation is completed and the sheet feeding operation is completed, a function of returning the next and subsequent sheets falling into the gap G formed between the sheet feeding roller 10 (idle roller 17) and the separation pad 13 to the sheet stacking surface 19. Have.

Here, the rotation of the return lever 18 is performed by a cam mechanism (not shown) interlocked with the rotation of the paper feed roller 10. The rotation trajectory of the return lever 18 is
A configuration is adopted in which the sheet P1 during printing does not enter the transport locus. In other words, the returning operation of the next and subsequent sheets P2 is performed below the conveyance locus of the sheet P1, so that the returning operation of the next and subsequent sheets P2 can be performed even during a series of sheet feeding operations. Can be done.

FIG. 3 shows the state of the sheet feeding device 1 after the sheet feeding operation is completed. The uppermost sheet P1 is conveyed while being pinched by the conveying roller 2 and the pinch roller 3. Printing is performed on P1 by the printing means 4. At this time, the paper feed roller 10 is stopped at the position shown in FIG.
The sheet is conveyed while being in contact with the idle roller 17.

On the other hand, FIG. 2 is an operation diagram of the main components of the sheet feeding device 1. When the sheet feeding is started, the driving force transmitted from a driving unit (not shown) causes the sheet feeding roller 10 to move as shown in FIG.
Starts normal rotation in the direction in which the sheet P is fed toward the printing unit 4. When the paper feed roller 10 reaches a certain angle, the pressure plate 11 operates to press the sheet P against the paper feed roller 10, and the return lever 18 is moved to a position where the conveyance of the sheet P is not obstructed so as to be opened. Start turning.

Thereafter, the sheet feeding roller 10 continues to rotate forward, and the sheet P is separated by the separation pad 13 accordingly. When the separation operation is completed, the return lever 18 starts the return operation, and thereafter, the pressure plate 11
Returns to the position before the start of the sheet feeding operation. When the sheet feeding roller 10 finally returns to the position before the start of the sheet feeding operation, the pressure plate 11 and the return lever 18 also return to the positions before the start of the sheet feeding operation. The sheet feeding operation is completed by the rotation of the sheet feeding roller 10 in one direction.

In this manner, the sheet feeding operation is performed by the feeding roller 1.
The rotation of the sheet P is completed by one rotation operation by the normal rotation of 0, and the operation of returning the sheet P to the stacking surface is performed at a specific timing during one rotation of the feeding roller 10, so that the sheet feeding device 1 (feeding Since the drive transmission to the feed roller 10) and the operation sequence can be simplified, the cost of the recording apparatus itself can be reduced.

Next, the sheet feeding operation of the sheet feeding device thus configured will be described.

FIG. 3 is a view showing a state before the sheet feeding operation of the sheet feeding apparatus 1 is started. At this time, the substantially linear portion 10b of the sheet feeding roller 10 is opposed to the separation pad 13, and this state is shown. At this time, the sheet P is set on the pressure plate 11. During this sheet setting, the pressure plate 11 is released from the paper feed roller 10 by the cam 16, so that a space for setting the sheet P is provided between the paper feed roller 10 and the pressure plate 11. .

At this time, the holder 14 to which the separation pad 13 is attached is configured so as not to move more than a predetermined amount in the direction approaching the paper feed roller 10 by a regulating portion (not shown). As described above, the idle roller 17 and the separation pad 13 are separated from each other.

On the other hand, the return lever 18 is on standby at a position where the locking portion 18a formed at the tip thereof is substantially perpendicular to the sheet stacking surface 19, so that the sheet stacking surface 19 and the pressure plate 11 The stacked and supported sheets P are prevented from falling into the avalanche into the gap G between the idle roller 17 and the separation pad 13. The locking portion 18a is provided at the distal end of the return lever 18 as described above,
, Also serves as a sheet drop prevention unit, thereby simplifying the configuration of the sheet feeding device 1 and simplifying an operation sequence and reducing costs.

Next, the paper feed roller 10 is
When rotation starts in the direction of the arrow around c, the cam 16 rotates in the releasing direction as shown in FIG. 4, and the rotation of the cam 16 causes the pressure plate 11 to receive the urging force of the spring 12 and The sheet P is urged toward the paper feed roller 10.

Thereafter, the uppermost sheet P1 of the stacked sheets P comes into contact with the circular arc portion 10a formed of the rubber member of the rotating paper feed roller 10, and
As a result, only the top sheet P1 or several sheets P including the next sheet P2 together with the top sheet P1 are guided to the sheet separation section 20, which is a nip section between the feed roller 10 and the separation pad 13. I will

On the other hand, the return lever 18 is
In association with the rotation of, the cam mechanism (not shown) is rotated and retracted to a position shown in FIG. Here, at this time, the leading end of the return lever 18 is located downstream (to the left in the drawing) of the sheet separating section 20, so that a later-described reliable return operation of the next sheet or the like can be performed. realizable.

Next, of the several sheets P guided to the sheet separating section 20, the next sheet P2 is separated by the separation pad 13 as described below, and as shown in FIG. Only the sheet P1 is fed.

That is, when the leading edge of the next sheet P2 abuts against the separation pad 13, its movement is inhibited, and the next sheet P2 is temporarily separated from the top sheet P1. Further, the frictional force between the arc portion 10a of the paper feed roller 10 and the uppermost sheet P1 is f1, and the next sheet P2
Assuming that the frictional force between the uppermost sheet P1 and the next sheet P2 is f3, and the frictional force between the uppermost sheet P1 and the next sheet P2 is f3, the paper feed roller is such that the relationship f1>f2> f3 is established. 10 and the separation pad 13, the uppermost sheet P <b> 1 and the next sheet P <b> 2 are pressed together by the arcuate portion 10 a of the sheet feeding roller and the separation pad 13 as the sheet feeding roller 10 rotates. In this state, the movement of the next sheet P2 is hindered by the frictional force f2 with the separation pad 13, and the sheet P2 is secondarily separated from the sheet P1.
Only the top sheet P1 is fed.

Next, as shown in FIG. 6, the top sheet P1 separated from the next sheet P2 in this way eventually has its leading edge conveyed by the conveying roller 2 and the pinch roller 3 as shown in FIG.
To be pinched. At this time, since the pressure plate 11 is rotated about the rotation shaft 11 a by the cam 16 and released, the urging force of the spring 12 does not act on the paper feed roller 10. Further, at this stage, the contact between the sheet P1 and the arc portion 10a of the sheet feeding roller 10 ends, and the sheet P1 comes into contact with the idle roller 17 gradually.

On the other hand, immediately before the contact between the sheet P1 and the arc portion 10a of the sheet feeding roller 10 is completed, the return lever 18
At the timing when the locking portion 18a vertically provided at the distal end protrudes above the separation pad 13 as shown in FIG.

When the paper feed roller 10 is further rotated, the sheet P1 comes into contact with the idle roller 17, whereby the idle roller 17 and the separation pad 13 are brought into contact.
Is formed between them. When the return lever 18 further rotates in the direction of the arrow with the rotation of the paper feed roller 10, the locking portion 18a of the return lever 18 appears in the gap G as shown in FIG. When the sheet P2 comes into contact with the next next sheet P2 and the rotation further proceeds, it acts on the sheets subsequent to the next sheet and pushes those sheets back to the sheet stacking surface 19.

As a result, the uppermost sheet P1 can be sent out, and even if the next and subsequent sheets including the sheet P2 fall into the avalanche in the gap G formed between the idle roller 17 and the separation pad 13. The sheet can be pushed back to the sheet stacking surface 19.

When the idle roller 17 comes into contact with the sheet P1, a gap G is formed between the idle roller 17 and the separation pad 13, and when the gap G is formed, the return lever 18 is moved to the gap G. And the next sheet including the sheet P2, which is another sheet that has entered the gap G together with the sheet P1 to be sent out, is pushed back to the sheet stacking surface 19, that is, at an arbitrary timing after the separation operation is completed, By pushing the next and subsequent sheets including P2 back to the sheet stacking surface 19, a reduction in throughput can be prevented with a simple structure.

After a series of these operations, the state shown in FIG. 1 is obtained. In this state, that is, when the sheet P1 is conveyed while being nipped by the conveying roller 2 and the pinch roller 3, Since the rear end of P1 is only in contact with the idle roller 17, the load applied to the sheet P1 is the resistance due to the contact between the sheet P1 and the sheet P2,
The resistance is only a few grams, such as the contact resistance of the idle roller 17 and the rotational sliding resistance of the idle roller 17, and no back tension is applied.

By preventing the back tension from being applied to the sheet P1, the influence on the sheet conveyance accuracy can be prevented, and the occurrence of disturbance in the printing accuracy in the printing means 4 can be prevented. Can be. Further, as a material for the transport surface of the transport roller 2, a rubber roller which is easily affected by a relatively backward resistance load can be used, so that the cost of the entire apparatus can be reduced.

In the above description, the configuration has been described in which the paper feed roller 10, the cam 16, and the return lever 18 are operated at independent and optimal timings, respectively. However, the present invention is not limited to this, and these may be configured to operate under a predetermined phase using a transmission mechanism such as a gear train or a belt drive.

Next, a second embodiment of the present invention will be described.

FIG. 8 is a side sectional view of a main part of an ink jet recording apparatus which is an example of an image forming apparatus provided with the sheet feeding apparatus according to the present embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

In the drawing, reference numeral 30 denotes a sheet feeding device, 31 denotes a return blade driving belt, and 33 denotes a return blade which is a thin plate as an example of a return unit. When it rotates in the direction, the return wing drive belt 31 rotates in the direction of arrow B around the pulleys 31a, 31b, and 31c.

In this embodiment, the return wing 33
Is a flexible thin plate having a thickness of several tens grams to 100
It has the property of being elastically deformed by a force of several tens of grams. Further, the phase of the paper feed roller 10 and the return wing 33 is such that when the paper feed roller 10 makes one rotation, the return wing 33 also returns to its original predetermined position. It is possible to push the next and subsequent sheets including the sheet P2 back to the predetermined stacking position at more appropriate timing.

On the other hand, reference numeral 32 denotes a drop-preventing lever which is a drop-preventing means provided with a locking portion 32a at the leading end thereof. The drop-preventing lever 32 is at the uppermost position when the sheet P is set. When the printing on the sheet P1 is completed and the next printing command is not sent to the recording apparatus main body 50, the apparatus waits at the position shown in FIG. ing.

As in the present embodiment, the return wings (return means) 33 and the prevention levers (drop prevention means) 32 are formed independently, so that a more reliable return operation can be performed. Thus, a highly reliable sheet feeding device can be provided.

Next, the sheet feeding device 30 configured as described above
Will be described.

Before the sheet feeding device 30 starts the sheet feeding operation, the sheet P is set on the pressure plate as shown in FIG. During this sheet setting, the pressure plate 11 is released from the paper feed roller 10 by the cam 16, so that a space for setting the sheet P is provided between the paper feed roller 10 and the pressure plate 11. . At this time, the holder 1
No. 4 is configured so that it does not move more than a specified amount in the direction approaching the paper feed roller 10 by a regulating unit (not shown).
As shown in FIG.
Are separated from each other, and a gap G is formed.

On the other hand, the drop-prevention lever 32 stands by at a position where the locking portion 32a vertically provided at the tip thereof is substantially perpendicular to the sheet stacking surface 19 as shown in FIG.
This prevents the sheets P stacked and supported on the sheet stacking surface 19 and the pressure plate 11 from falling into the gap G in an avalanche. At this time, the return wing 33 is located at the position shown in the same drawing, and is in a state of not exerting any action on the sheet P.

Next, the paper feed roller 10 is
When the rotation starts in the direction of arrow A about c, the cam 16 rotates in the release direction as shown in FIG. 9, and the rotation of the cam 16 causes the pressure plate 11 to receive the urging force of the spring 12, The sheet P on the pressure plate is urged toward the paper feed roller 10.

Thereafter, the uppermost sheet P1 of the stacked sheets P comes into contact with the circular arc portion 10a formed by the rubber-like member of the rotating paper feed roller 10, and
Thereby, only the top sheet P1 or several sheets P including the next sheet P2 together with the top sheet P1 are guided to the sheet separation section 20.

On the other hand, at the same time, the fall prevention lever 32
Starts rotating in the direction of arrow C.
No contact with 1. Also, the return wing 33 is
It moves with the return blade drive belt 31 moving in the direction, but does not act on the sheet P at this stage.

Next, of the several sheets guided to the sheet separating section 20, the next sheet P2 is separated from the top sheet P1 by the separation pad 13, and only the top sheet P1 is fed. Is done. Thereafter, the leading edge of the uppermost sheet P1 separated from the next sheet P2 is pressed by the transport roller 2 and the pinch roller 3 as shown in FIG.

At this time, since the pressure plate 11 is rotated by the cam 16 about the rotation shaft 11a and released,
The urging force of the spring 12 does not act on the paper feed roller 10. At this stage, the sheet P1 and the sheet feed roller 1
0, the contact of the arc portion 10a ends, and gradually the sheet P1
Comes into contact with the idle roller 17.

On the other hand, the return wing 33 is
1 and the sheet P1 moves as shown in FIG.
Immediately before the contact between the sheet P1 and the arcuate portion 10a of the sheet feeding roller 10 ends, the engaging portion 32a at the leading end and the back surface of the sheet P1 start contacting. However, at this time, since the surface of the sheet P1 is in contact with the arc portion 10a of the sheet feeding roller 10, the return wing 33 is in a buckled state because it cannot push up the sheet P1.

Here, when the paper feed roller 10 is further rotated, the sheet P1 comes into contact with the idle roller 17, whereby the idle roller 17 and the separation pad 13 are brought into contact.
Is formed between them. Further, when the return wing 33 moves further in the direction of the arrow than the state of FIG. 10 with the rotation of the paper feed roller 10, the leading end of the locking portion of the return wing 32 contacts the back surface of the sheet P1 as shown in FIG. , Contacts the next sheet P2 located below the sheet P1.

When the return blade 32 further moves in this state, it acts to push back the next and subsequent sheets to the sheet stacking surface 19 as shown in FIG. Accordingly, the uppermost sheet P1 can be sent out, and even if the next and subsequent sheets including the sheet P2 fall into the avalanche into the gap G formed between the idle roller 17 and the separation pad 13, this sheet P1 The sheet loading surface 19
Can be pushed back.

FIG. 13 shows a state in which a series of paper feeding operations has been completed and the printing operation is ready. That is,
All the sheets subsequent to the next sheet are pushed back to the sheet stacking surface 19, and the return blades 33 return to the same position as the start of the sheet feeding operation. After that, when the trailing edge of the sheet P1 is ejected from the sheet feeding device 30, if the next print command does not come, the fall prevention lever 32 rotates in the direction of arrow CC shown in FIG. It returns to the state of FIG.

Here, in this state, that is, when the sheet P1 is being conveyed while being nipped by the conveying roller 2 and the pinch roller 3, the resistance force due to the contact between the sheet P1 and the sheet P2 at the rear portion of the sheet P1. In addition, the sheet P1 receives the contact resistance between the sheet P1 and the idle roller 17 or the rotational sliding resistance of the idle roller 17, but since each has a resistance of about several grams, no back tension is applied. The influence on the accuracy can be prevented, and the occurrence of disturbance of the printing accuracy in the printing means 4 can be prevented.

[0092]

As described above, when the rotating body which comes into contact with the sheet instead of the sheet feeding means at the position corresponding to the notch of the sheet feeding means as in the present invention, this rotation is performed. A gap is formed between the body and the separating means, and when the gap is formed, the return means is caused to appear in the gap so as not to enter the sheet conveyance locus, and the other sheets entering the gap are stacked on the sheet. By pushing the sheet back to the sheet stacking unit, another sheet can be returned to the sheet stacking unit with a simple structure without affecting the sheet feeding operation, and a decrease in throughput can be prevented. Further, it is possible to prevent the back tension from being applied to the fed sheet, and it is possible to prevent the influence on the sheet conveyance accuracy.

[Brief description of the drawings]

FIG. 1 is a side cross-sectional view of a main part of an inkjet recording apparatus as an example of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is an operation diagram of main parts of the paper feeding device.

FIG. 3 is a diagram illustrating a state before the paper feeding device starts a paper feeding operation.

FIG. 4 is a diagram showing a state when a paper feed roller of the paper feed device starts rotating.

FIG. 5 is a diagram illustrating a state in which only the top sheet is fed among several sheets guided to a sheet separation unit of the sheet feeding device.

FIG. 6 is a diagram illustrating a state in which the leading end of the uppermost sheet is nipped by a conveyance roller and a pinch roller.

FIG. 7 is a diagram illustrating a state in which a return lever of the sheet feeding device starts to contact a next sheet positioned below an uppermost sheet.

FIG. 8 is a side sectional view of a main part of an ink jet recording apparatus as an example of an image forming apparatus including a sheet feeding device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a state before the paper feeding device starts a paper feeding operation.

FIG. 10 is a diagram illustrating a state in which the leading edge of the uppermost sheet is nipped by a conveyance roller and a pinch roller.

FIG. 11 is a diagram illustrating a state in which the leading end of a locking claw of a return blade of the sheet feeding device starts to contact a next sheet positioned below an uppermost sheet.

FIG. 12 is a diagram illustrating a state in which a return blade of the sheet feeding device pushes a next sheet back to a sheet stacking surface.

FIG. 13 is a diagram illustrating a state in which a series of sheet feeding operations of the sheet feeding device has been completed, and preparation for a printing operation has been completed.

FIG. 14 is a diagram showing a configuration of a sheet feeding device using a conventional pad separation system.

FIG. 15 is an operation diagram of main parts of the conventional paper feeding apparatus.

[Explanation of symbols]

 1, 30 paper feeder 4 printing unit 10 paper feed roller 10a arc portion (of paper feed roller) 10b substantially linear portion (of paper feed roller) 11 pressure plate 13 separation pad 16 cam 17 idle roller 18 return lever 20 sheet separation unit 31 Returning blade drive belt 32 Returning blade 33 Fall prevention lever 50 Recording device main body G Clearance P Sheet P1 Top sheet P2 Next sheet

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Yoshino 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yasuyuki Asai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Jun Katayanagi 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 3F343 FA02 FA06 FA09 FA17 FB02 FB03 FB04 FC01 FC06 GA03 GB01 GC01 GD01 HA12 HB01 HD18 JA16 JD03 JD08 JD33 LA04 LA15 LC14 LC19 LD26

Claims (10)

[Claims] 1. A sheet feeding device for separating and feeding sheets stacked one by one in a state of being inclined to a sheet stacking section, wherein the sheet stacked on the sheet stacking section is sent out and abuts on the sheet. A feeding means having a notch formed on an outer peripheral surface thereof, rotatably provided coaxially with the feeding means, and replacing the feeding means at a position corresponding to the notch of the feeding means. A rotating body that comes into contact with the sheet, a sheet that comes into contact with the sheet fed by the feeding unit, separates the sheets one by one, and a gap between the rotating body and the rotating body while the rotating body contacts the sheet. A separating unit configured to form a sheet, and when a gap is formed between the separating unit and the rotating body, the sheet appears in the gap and pushes another sheet that has entered the gap back to the sheet stacking unit. And return means, The sheet feeding device, wherein the writing-back means appears in the gap within a range that does not enter the conveyance locus of the conveyed sheet. 2. The sheet feeding device according to claim 1, wherein a diameter of the rotating body is smaller than a diameter of the feeding unit so as to form the gap. 3. The sheet feeding device according to claim 1, wherein the separating unit is configured to be in pressure contact with an outer peripheral surface of the feeding unit, but not to contact the rotating body. 4. The return means is a return lever which appears in the gap in conjunction with a sheet feeding operation of the sheet feeding means and moves in a direction to return the sheet to a sheet stacking unit. The paper feeding device according to claim 1. 5. The sheet feeder according to claim 4, wherein the return lever also functions as a unit for preventing sheets stacked in the sheet stacking section from being dropped into the gap. 6. The return means is provided on a belt that rotates at a constant cycle in conjunction with a sheet feeding operation of the feed means and appears in the gap, and returns the sheet to the sheet stacking unit. The sheet feeding device according to claim 1, wherein the sheet feeding device is a moving thin plate. 7. The sheet feeding device according to claim 6, wherein the thin plate is flexible so as to bend while being in contact with an outer peripheral surface of the feeding unit before the gap is formed. . 8. The sheet feeding device according to claim 6, further comprising means for preventing sheets stacked on the sheet stacking portion from being inclined in the gap. 9. The operation of separating and feeding the sheets one by one is completed by one rotation operation of the feeding unit in one direction.
The sheet feeding device according to claim 1, wherein the operation of returning the other sheet to the sheet stacking unit is performed at a specific timing during one rotation of the feeding unit. 10. An image forming apparatus comprising: an image forming unit; and a sheet feeding device that feeds a sheet to the image forming unit, wherein the sheet feeding device is any one of claims 1 to 9. An image forming apparatus, characterized in that: