JPH0717652A - Sheet feeder - Google Patents

Abstract

PURPOSE:To feed a sheet material surely separated even when it is a sheet material having strong adhesion and attraction by static electricity or a sheet material having a high friction coefficient. CONSTITUTION:A sheet sheaf on a sheet loading base 4, at each paper feed, is brought into contact with a kick roller 7 to deliver a sheet, and the delivered sheet is fed by a separation conveying roller 8 and further given friction conveying force in a reverse direction to a delivery direction by a separation reverse roller 9 opposed to this separation conveying roller. After nipping a sheet point end by the paired separation rollers 8, 9, by applying press return force in a reverse direction to a feed direction relating to the sheet in a side of the separation reverse roller 9 by a paddle 10, the sheet is prevented from being fed together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus useful for a copying machine, a recording apparatus and the like, and more particularly to a sheet feeding apparatus capable of separating even sheets having strong adhesion and suction. .

[0002]

2. Description of the Related Art Generally, some sheets to be handled in a copying machine, a recording apparatus, etc. have extremely strong adhesion between sheets and adsorption by static electricity, such as a transparent muller sheet for OHP. Conventionally, when handling such OHP sheets, when the sheets are conveyed by using a cassette, they are double-fed, and thus they are fed manually one by one.

On the other hand, as a general sheet separating apparatus, conventionally, a document feeding apparatus for separating a sheet one by one by vertically moving a sheet placing table (hopper) each time a sheet is fed (Japanese Patent Laid-Open No. 55-111958). Gazette) or if the sheet is not detected downstream of the sheet feeding operation within a predetermined time after the sheet feeding operation, the entire form stacked on the sheet mounting table is once lowered to separate the sheet, and then the sheet is raised again. There is known a form feeding device which re-feeds the sheet (Japanese Patent Laid-Open No. 58-51859).
Issue).

[0004]

However, in the sheet separating apparatus in the conventional sheet feeding apparatus, the above-mentioned sheet having high adhesion, for example, a transparent muller sheet for OHP is fed, or a sheet once copied. When a document is fed by a document feeder or the like, the separation of the sheets becomes insufficient due to the influence of static electricity, etc., and so-called double feed occurs in which two or three sheets are overlapped and fed.

Therefore, an object of the present invention is to solve the above-mentioned problems and reliably separate and feed even a sheet material having a strong adhesion and a strong adsorption by static electricity or a sheet material having a high friction coefficient. It is to provide a sheet feeding device capable of performing the above.

[0006]

In order to achieve the above-mentioned object, a sheet feeding device of the present invention is provided with a feeding means for feeding out the sheets stacked on a mounting table, and facing the feeding means. After the reverse means for giving a conveying force to the fed sheet in a direction opposite to the feeding direction and the leading end of the fed sheet have passed the position where the feeding means and the reverse means are nipped, the sheet on the reverse means side is fed. On the other hand, a push-back means for applying a push-back force in a direction opposite to the feeding direction is provided (Claim 1).

Further, in the present invention, a sheet placing table on which stacked sheets are placed and moved up and down, feeding means for feeding the sheet in contact with the sheet when the sheet placing table is raised, and downstream of the feeding means. And a conveying means for conveying the sheet to be fed out, a reverse means provided opposite to the conveying means for giving a conveying force in a direction opposite to the sheet feeding direction, and a pushing means for pushing back the sheet on the reverse means side. The push-back means for applying force and the interlocking means for operating the push-back means together with the lowering operation of the sheet placing table after the sheet leading edge has passed the position where the sheet is nipped by the conveying means and the reverse means are provided. (Claim 2)

The pushing-back means is a rotary paddle provided on the same shaft as the separating reverse roller via a torque limiter (claim 3), and further, paddle lock claws for preventing the rotation of these rotary paddles. It is possible to prevent the paddle rotation by the paddle lock claw and to release the paddle rotation with the vertical movement of the sheet mounting table (claim 4). The push-back means may be a rotary paddle provided on the separate shaft from the separation reverse roller (claim 5) or a swing lever provided on the separate shaft from the separation reverse roller (claim 6). .

[0009]

According to the first aspect of the invention, the sheets stacked on the mounting table are fed out by the feeding means, and the leading end of the sheet is nipped between the feeding means and the reversing means which faces the feeding means. After the sheet front end passes through the nip position, the push-back means applies a push-back force to the sheet on the reverse means side in the direction opposite to the feeding direction. Therefore, even if two or more sheets are unfortunately nipped between the feeding means and the reverse means, the sheet on the reverse means side is pushed back by the reverse means in the direction opposite to the feeding direction. Only the sheet on the side of the feeding means is fed in the forward direction. As a result, even if the sheets have strong adhesion, such as OHP sheets, complete sheet separation is performed for each sheet.

Here, the "feeding means" may have a structure having a portion for feeding out the sheets stacked on the mounting table and a portion facing the reverse means, for example, two portions of a kick roller and a conveying roller. Of course, including the form provided,
Even in the case of one roller, a part thereof in the circumferential direction is taken out and the other part in the circumferential direction is opposed to the reverse means (the above-mentioned kick roller and feeding roller are used in combination). May be. On the other hand, the "reverse means" may be any means as long as it cooperates with the conveying means and consequently exerts a pushing-back force on the sheet in a direction opposite to the conveying direction. Therefore, not only the rotating roller but also the pad or the like is stationary. It may be an existing member. Further, “opposing” includes both a case where the conveying means and the reverse means are opposed to each other while partially overlapping with each other when viewed from a direction intersecting the conveying direction, and a case where they are in contact with each other.

Further, the "push-back means" may be any means that applies a push-back force to the reverse means side of the sheet whose leading edge has passed the nip position. To grasp that the sheet leading edge has passed the nip position, for example, as shown in FIG. 1, the sheet leading edge detection sensor may be used to grasp the time when the sheet leading edge moves slightly downstream from the nip position. It may be grasped by utilizing the fact that the rotating load changes. The time point at which the push-back force is applied is related to the configuration of the push-back means and the magnitude of the push-back action force, but in short, it eliminates the occurrence of a state in which the desired sheet cannot be fed and tries to be double-fed. It is possible to push back an extra sheet, and it is more effective at an early stage in terms of timing.

According to the second aspect of the invention, when the sheets are fed, the sheet mounting table is raised and the surface of the sheet bundle is brought into contact with the feeding means. As a result, the sheet is fed out and nipped between the next conveying means and the reverse means. In this separating unit, since the reverse means applies the conveying force in the opposite direction to the sheet, even if the sheet is double-fed, if it is a normal sheet, only the first sheet will move to the separating unit. After passing, the second and subsequent sheets are stopped at the upstream surface of the separation reverse roller in the sheet conveying direction, especially near the upper portion thereof. However, in the case of a sheet having strong adhesion such as an OHP sheet, there is an inconvenient situation in which the first sheet and the second and subsequent sheets are passed while being nipped between the conveying means and the reverse means. Occurs.

However, when the leading edge of the sheet passes the position where it is nipped by the conveying means and the reverse means, the push-back means is operated by the interlocking means as the sheet placing table is lowered, and the push-back means is moved to the sheet on the reverse means side. A pushing back force is applied to it. For this reason, the second and subsequent sheets that are passing are pushed back by this pushing-back means, and as a result, only the first sheet passes between the transport means and the reverse means. On the other hand, since the lowering operation of the sheet placing table is being performed, the second and subsequent sheets are moved downward accordingly, and there is a gap between the first sheet and the second and subsequent sheets. A large air layer is formed. That is, the separation between the first sheet and the second and subsequent sheets is complete.

Therefore, even if the sheet has a strong adhesiveness such as an OHP sheet or a sheet having a strong absorptive property that has been once copied, the sheets can be reliably separated from each other, and it is possible to prevent the sheet from being fed. .

According to a third aspect of the present invention, the push-back means is provided on the separation reverse roller shaft so as to be a rotary type, and further, according to the fourth aspect, the rotation of the paddle is prevented and released by interlocking with the vertical movement of the sheet mounting table. , A simple structure can be obtained. Further, as described in claims 5 and 6, the desired structure can be dealt with by using the push-back means as a rotary paddle or rocking lever provided on a separate shaft from the separation reverse roller.

[0016]

The present invention will be described below with reference to the illustrated embodiments.

In FIG. 1, reference numeral 1 is a sheet feeding cassette for OHP sheets, inside which a conveying support plate 2 is arranged so as to divide an internal space into upper and lower parts, and a rear end portion (upstream) of the sheet feeding direction (upstream). The section from the edge) to the middle part is used as the stationary side of the sheet mounting table. An intermediate portion of the transport support plate 2, that is, a portion that supports the front half portion of the sheet bundle is formed as an inclined recessed portion 3 having a deeper front end side (downstream side) in the sheet feeding direction, and a movable sheet mounting portion is formed below the inclined recessed portion 3. The table 4 is arranged. The sheet mounting table 4 is supported by a rotating shaft 4a disposed near the inclination start portion of the recessed portion 3, and an elevating drive lever 6 is provided on the upstream side of the sheet mounting table 4 in the sheet feeding direction. It is arranged. By pushing down the lever 5 composed of a leaf spring slantingly hung from the rotation shaft 4a of the sheet mounting table 4 by the lifting drive lever 6,
The sheet mounting table 4 rotates about a rotation shaft 4a, and at this time, the entire sheet mounting table 4 passes through an opening 2A provided in the recess 3 of the transport support plate 2 so that the leading end thereof is lifted obliquely upward. It has become.

A kick roller 7 as a feeding means is provided above the recess 3 so that the leading end of the lifted sheet placing table 4 may come into contact with the kick roller 7. Further, on the downstream side of the recessed portion 3 in the sheet feeding direction, a separating and conveying roller 8 as a conveying means is disposed above the conveying support plate 2, and the feeding means and the conveying means constitute a feeding means. ing. A separation reverse roller 9 as a reverse means is arranged below the conveyance support plate 2 so as to face the separation conveyance roller 8, and the separation conveyance roller 8 and the separation reverse roller 9 together form a separation section. . In this embodiment, the rollers 8 and 9 are arranged in a vertically overlapping relationship with each other without contact, and when viewed at this overlapping portion, the separating / conveying roller 8 has a frictional conveying force in the forward direction with respect to the sheet feeding direction. Is applied to the sheet, and the separation reverse roller 9 applies a frictional conveyance force in the direction opposite to the feeding direction to the roller 9
Rotate in the direction to give to each side sheet. Specifically, both rollers are rotated in the same counterclockwise direction.

In the case of the present embodiment, as shown in the expanded axial position of FIG. 2, one separation / conveyance roller 8 is provided at the center of the shaft 8a, while the separation reverse roller 9 is provided with its shaft 9a. Two of them are provided so that a part of the lower part of the separation / conveyance roller 8 is inserted between the separation reverse rollers 9 and 9, and when viewed in the axial direction, both rollers 8 and 9 are part of each other. Are overlapping. The upper part of the separation reverse roller 9 is partially exposed from the transport support plate 2.

Further, a paddle 10 as a sheet pushing-back means described later is provided on the side of each of the separation reverse rollers 9 coaxially with the separation reverse roller shaft 9a. In the case of the present embodiment, the paddle 10 is composed of a rotary paddle attached to the separation reverse roller shaft 9a via a spring type torque limiter 13, and the paddle body 11
The shape is inclined obliquely rearward in the rotational direction from a position radially outward from the shaft 9a, and its front surface functions as a return action surface. This paddle body 11
Like the separation reverse roller 9, has a length such that its tip is partially exposed from the notch 2B of the transport support plate 2. Further, the paddle 10 has a locking portion 12 on the peripheral surface of the boss portion for holding the paddle body 11 at the retracted position which does not hinder the feeding as shown in FIG. 1, and the locking portion 12 has a paddle lock as an interlocking means. The tip claw portion 15 of the claw 14 is adapted to be engaged.

The paddle lock claw 14 is swingably supported by the shaft 16 and is pulled by the spring 17, so that FIG.
Therefore, the habit of turning counterclockwise is always given. However,
The shaft 16 of the paddle lock claw 14 is located within the radius of the rotation trajectory drawn by the tip of the sheet mounting table 4 described above. Therefore, the paddle lock claw 14 has its tip when the sheet mounting table 4 descends from above. The paddle 10 is pressed by a portion to move to a disengaged position shown by a chain line in FIG. 1 to release the paddle 10. The lowering of the sheet mounting table 4 is performed immediately after the leading edge of the uppermost sheet is nipped by the roller pair of the separating section or slightly after that.

FIG. 2 shows the drive system of the three rollers 7, 8, 9 and the elevating drive lever 6 in an expanded form. The shaft 6a of the lifting drive lever 6, the shaft 7a of the kick roller 7, the shaft 8a of the separation conveyance roller 8, and the shaft 9a of the separation reverse roller are
They are supported by machine frames 18 and 19 on both sides,
It is driven by a single drive motor 20 common to these. That is, the lifting drive lever shaft 6 a is rotated on the machine frame 18 side by the main gear 22 rotated by the drive motor 20 via the belt 21 via the gear 23 and the torque limiter 24. Further, the kick roller shaft 7a is connected to the gear 22.
Is rotationally driven via a gear 25 and a one-way clutch 26 which are engaged with the gear 22, or gears 27 and 28 which are engaged with the gear 22 and a one-way clutch 29. On the machine frame 19 side,
The kick roller shaft 7a, the separation conveyance roller shaft 8a, and the separation reverse roller shaft 9a have gears 30, 32, and 34, respectively.
Are attached, and these are sequentially connected in series via intermediate gears 31 and 33 provided therebetween. Therefore, the separation conveyance roller shaft 8a and the separation reverse roller shaft 9
a is rotated in sequence by the rotation of the kick roller shaft 7a, and the three roller shafts 7a, 8a, 9a are operated by the one-way clutches 26, 29, and the forward and reverse rotations of the drive motor 20 are as shown in FIG. Rotate forward in the direction indicated by the arrow.

Returning to FIG. 1, the sheet placing table 4 is provided with an empty detection sensor (empty sensor) 35 for detecting the absence of a sheet on the sheet placing table, and the pair of separating rollers 8 and 9 are provided. A sheet leading edge detection sensor 36 is provided on the downstream side (front side) in the sheet conveying direction. These sensors 35, 36 are, for example, contact sensors. Signals from these sensors are input to a control device (not shown) mainly including a microprocessor, and the control device controls the drive motor 20 and the like.
A pickup roller 37 of the main body of the copying machine is arranged further to the front side than the sheet leading edge detection sensor 36 in the sheet feeding direction.

Next, the operation of the above configuration will be described with reference to the control flow of FIG.

First, as shown in FIG. 3, the sheet bundle 40 is set. As a result, the sheet mounting table 4 rotates about the shaft 4a to lower the leading end side, and the empty detection sensor 3
5 turns on.

Now, when the copy button of the copying machine is turned on (step 41), the empty detection sensor 35 in the control device is turned off.
Since it is confirmed that it is in the N state, the program of the control device proceeds to step 43 of FIG. 7 and causes the drive motor 20 to rotate normally (steps 42 to 43).

As a result, the kick roller 7, the separation / conveyance roller 8 and the separation reverse roller 9 are rotated in the forward direction as shown by the arrow in FIG. Further, the elevating drive lever 6 rotates clockwise in FIG. 1 to push down the lever 5 and rotate the sheet mounting table 4 counterclockwise about the rotation shaft 4a. As shown in FIG. Is increased (step 44). Due to the action of the torque limiter 24, the surface of the sheet bundle 40 contacts the kick roller 7 with an appropriate pressure contact force.

The sheet placing table 4 rises and the paddle lock claw 1
4 away from the paddle lock claw 14 causes the spring 17
4, the tip claw portion 15 is engaged with the locking portion 12 of the paddle 10 by being pulled counterclockwise in FIG. That is,
The kick roller 7, the separation conveyance roller 8, and the separation reverse roller 9 are rotated in the normal direction, but the paddle 10 (torque limiter provided) is locked by the paddle lock claw 14 and stopped at the retracted position. At this time, if the paddle 10 is rotating, the sheet material will not enter the nip portion of the separating portion.

By contacting the kick roller 7, the first uppermost sheet 40a of the sheet bundle 40 is fed out,
It is nipped between the next separation conveyance roller 8 and the separation reverse roller 9. In this separation unit, the separation reverse roller 9 applies a conveyance force in the opposite direction to the sheet. Therefore, even if the sheet is double-fed, if the sheet is a normal sheet, the separation conveyance roller 8 separates from the sheet. Reverse roller 9
Due to the difference in frictional force between the uppermost sheet 40 and the uppermost sheet 40 as shown in FIG.
A is fed by the separation / conveyance roller 8 in the sheet conveying direction by a frictional force, and its tip passes through the separation roller pair 8 and 9.
However, the second and subsequent sheets below it cannot pass through the pair of separating rollers 8 and 9, and the leading edge of the sheet is on the upstream side surface of the separating reverse roller 9 in the sheet conveying direction, especially near the upper portion thereof. It will be in a stopped state (Fig. 5).

However, in the case of an OHP sheet bundle having strong adhesion, one or more lower sheets following this are pulled out together, and in the succeeding separating roller pairs 8 and 9,
The uppermost sheet 40a and the sheet below this are nipped, and start to pass while being nipped between the separation conveyance roller 8 and the separation reverse roller 9. But the top sheet 4
When the leading edge of 0a passes the sheet leading edge detection sensor 36,
As described below, the paddle 10 operates to push back the lower sheet.

First, when the leading edge of the uppermost sheet 40a passes the sheet leading edge detection sensor 36 (step 45), the control device causes the drive motor 20 to rotate in the reverse direction, and the sheet placing table 4 is lowered as shown in FIG. 6 (step). 46). However,
Even if the drive motor 20 is rotated in the reverse direction, the force transmission path to the kick roller 7 is changed from the system including the clutch 26 to the clutch 29.
However, the rotation directions of the kick roller 7, the separation conveyance roller 8, and the separation reverse roller 9 do not change, and the forward rotation indicated by the arrow in FIG. 4 is continued (step 4).
7).

The tip of the lowered sheet placing table 4 pushes down the paddle lock claw 14 which is the interlocking means, so that the paddle lock claw 14 is disengaged from the paddle 10.

As a result, the rotation-prevented state of the paddle 10 is released (step 48), the paddle 10 rotates along with the shaft 9a (step 49), and a pushing-back force is applied to the sheet on the reverse means side which is passing. . Therefore, the sheet on the reverse means side that is passing is pushed back by the paddle 10 and only the first sheet passes between the separation conveyance roller 8 and the separation reverse roller 9. The pushed back sheet falls on the sheet bundle of the sheet placing table 4 located below together with the sheet that remains in sliding contact with the separation reverse roller 9. As a result,
An air layer portion 38 shown by hatching in FIG. 6 is generated between the uppermost sheet 40a and the second and subsequent sheets, and the sheets are reliably separated. Therefore, even a sheet having a strong adhesion such as an OHP sheet or a sheet having a strong absorptivity that has been once copied can be reliably separated and fed.

After that, the drive motor 20 is stopped and the main body pickup roller 37 of the copying machine is rotated (steps 50 and 51). The control device uses the sheet leading edge detection sensor 36.
Is confirmed to be turned off (step 52), and the sheet feeding control is ended.

In the above embodiment, the push-back means is the rotary paddle 10 provided coaxially with the separating reverse roller 9 and the paddle body 11 is only one, but the present invention is not limited to this. Instead, the sheet may be of any form that can give a pushing-back action to the sheet on the reverse means side of the sheet nipped by the pair of separation rollers. Therefore, as illustrated in FIG. 8, at least an angle range of θ = 30 to 45 ° in the front-rear direction on the facing surface side of the separation reverse roller 9, and preferably θ = 30 to 45 ° on the facing surface side of the separation reverse roller 9. In addition to the angular range of, the paddles that are moved so as to move in the direction opposite to the sheet feeding direction over the range of D = 60 to 45 ° up to the immediate side may have any other structure. Can be used.

FIG. 9 shows the paddle 10 with the angle range 2θ.
Arc segment 55 having a notch in the opening range sandwiching + D
It is the same as the case of FIG. 1 in that it is a rotary paddle provided coaxially with the separation reverse roller 9. In the case of the paddle of the embodiment of FIG. 9, the cutout flat surface portion 56 of the arc segment 55 acts as the paddle body 11. The rotary paddle is also provided with a locking portion 12 as a recess, and the paddle lock claw 14 can be used to interlock with the vertical movement of the sheet mounting table 4, which is the sheet mounting table, to prevent and release the paddle rotation.

10 and 11 show an embodiment in which the support shaft 57 of the paddle 10 is different from the shaft 9a of the separating reverse roller 9. In the case of this embodiment, the support shaft 57 of the paddle 10
Is located within the range of the angle region 2θ + D, and the paddle body 11 projects and passes through the peripheral surface of the separating reverse roller 9 in the angle region 2θ + D only when the paddle body 11 acts, and the second and subsequent sheets are about to be fed. And push back the remaining seats.

FIG. 12 shows a swing lever 58 which does not rotate one full 360 degrees, and a curved surface 59 at the tip of the swing lever 58 has the angle region θ.
It is provided so as to project from the peripheral surface of the separation reverse roller 9 and pass in the range of + D (or 2θ + D).
In the case of this embodiment, the swing center shaft 58a of the swing lever 58
Is in front of and below the separation roller pair 8 and 9 as viewed in the sheet conveying direction, and therefore, the tip end curved surface 59 of the rocking lever 58 is provided.
Is larger than the diameter of the separating reverse roller 9. The electromagnetic solenoid 60 can be used to switch the paddle rocking lever 58 between the operating position in which it projects from the peripheral surface of the separation reverse roller 9 and the non-operating position in which it does not project. This is similar to the above description. It can be linked to vertical movement.

In the above-described embodiment, the entire sheet mounting table 4 is configured to pass through the opening 2A provided in the concave portion 3 of the transport support plate 2 and the tip end is lifted obliquely upward. The shape and size may be such that only the vicinity of the central portion of the sheet placed on the transport support plate 2 is diagonally lifted when viewed in the width direction. According to this structure, the sheet bundle is swung up and down while being supported from below in the vicinity of the center of the width of the sheet bundle. Therefore, the degree of restraint of the entire sheet bundle is weakened, and the sheet bundle can be brought into a so-called “split” state. Is obtained.

By the way, in the above embodiment, the case where the above-mentioned feeding means is composed of the kick roller 7 and the separation / conveyance roller 8 has been described, but the feeding means may be composed of one roller. For example, the upper surface of the sheet bundle tip portion is pressed against the inlet side peripheral surface of the separation / conveyance roller 8, and the sheet fed in the circumferential direction of the separation / conveyance roller 8 due to the frictional force of the separation / conveyance roller 8 is pressed from the pressing position of the same separation / conveyance roller 8. May be nipped between the separation / conveyance roller 8 and the separation reverse roller 9 facing the separation / conveyance roller 8 on the downstream side in the feeding direction. In such a form, the kick roller 7 as in the embodiment of FIG.
The kick roller 7 can be omitted.

In the above embodiment, the sheet leading edge detection sensor 36 detects the time when the sheet leading edge moves slightly downstream from the nip position. However, the nipping point is detected, and the operating point is based on this point. Can also be determined. The "nip point" can be detected as follows.

13 to 15 show "at the time of nipping"
This is an example in which is understood from the fluctuation of the load.

FIG. 13 shows the construction of the paper feed section 80 in the automatic document feeder 70 of the electronic copying apparatus C. A pickup roller 81 serving as a feeding means for feeding out the document sheet of the paper feed tray 71, and the pickup roller 8 are shown.
It is composed of a separation roller 86 that feeds the original sheet fed out from sheet No. 1 in the feeding direction, and a separation pad 87 that comes into contact with the separation roller 86 and prevents the second and subsequent sheets from advancing. Also in this embodiment, the separation roller 86 constitutes a feeding means together with the pickup roller 81, and in relation to the separation pad 87, a separation portion 85 for separating the original sheets one by one together with the separation pad 87. I am configuring. The separation pad 87 is held by a pad holder 88, and is pressed toward the separation roller 86 by a holding spring 89 that acts on the pad holder 88. Although the separation pad 87 is a stationary member, it functions as a reverse unit that applies a conveying force in a direction opposite to the above-described sheet feeding direction in relation to the separation roller 86.

In this embodiment, the paddle 10 as the above-mentioned push-back means is not shown, but is mounted on the side of the separation pad 87 which is the reverse means in the same manner as above.

The sheets stacked on the paper feed tray 71 are taken out one by one or a plurality of sheets from the lower side by the pickup roller 81, and only the lowest sheet is separated by the separating section 85 including the separating roller 86 and the separating pad 87. And sent out to the reversal space section 93. During the separating operation, when the original sheet is fed by the pickup roller 81, the sheet 62 is pushed downward from above by the weight plate 83 by the driving means 62 such as a solenoid to increase the frictional force to increase the sheet conveying force. It is obtained and sent to the separation roller 86. Reference numeral 82 is a sheet empty sensor, and 97 is a registration sensor.

The pickup roller 81, the separation roller 86 and the registration roller 95 are driven by a drive motor MOT1 which is a common DC motor, and the rotation amount thereof is detected by an encoder E. The control device 63 monitors the magnitude of the load applied to the drive motor MOT1 by receiving a signal from the load detection means 61, and when the load changes from large to small, the driving means 62 for pressing the weight plate 83. Is returned to the OFF state, whereby the pressing operation of the weight plate 83 is released.

FIG. 14 shows a specific configuration of the control device 63.

The drive motor MOT1 is inserted in the collector output circuit of the transistor 64 which is turned on / off by a signal from the CPU. The above-mentioned load detecting means 61 is composed of a detecting resistor 65 inserted in the emitter circuit of the same transistor, and a voltage comparator 66 for comparing the terminal voltage Vi of this detecting resistor 65 with the reference voltage VR. . The pressing operation drive means 62 for causing the weight plate 83 to perform the pressing operation is composed of an electromagnetic solenoid 67 and a drive transistor 68 thereof.

Next, the operation will be described.

When an original sheet is placed on the paper feed tray 71 and the copying machine C is started (point a in FIG. 15),
The solenoid 67 in the pressing operation drive means 62 is activated (turned on), and the weight plate 83 is moved to the pickup roller 81.
Press it against the side. Further, an ON signal is generated for the transistor 64, and the drive motor M for the pickup roller 81 is
The OT1 starts to rotate in the forward direction, and sends the lower sheet of the original sheet bundle toward the separating section 85. At this time, at the same time, the solenoid (not shown) of the stopper 84 also operates to stop the stopper 84.
Lower down.

Here, while the sheet does not reach the nip portion between the separation roller 86 and the separation pad 87 (a, b in FIG. 15).
In the interval), the separation roller 86 and the separation pad 87 rub directly. Since the friction coefficient between the separation roller 86 and the separation pad 87 is larger than the friction coefficient between the original sheet and the separation pad 87, the drive motor MO that drives the separation roller 86.
The load of T1 increases and the load current also increases as a characteristic of the DC motor (H in FIG. 15). Also, the weight plate 8
The sheet bundle pressed by the pickup roller 81 by 3 is fed out by the rotation of the pickup roller 81 due to the increase in the frictional force between the sheet and the pickup roller 81 due to the pressing.

At this time, usually one or more sheets are sent out, but they are blocked by the separation pad 87 pressed against the separation roller 86, and only the lowermost original sheet is sent out.

When the original sheet slips between the separating roller 86 and the separating pad 87, the frictional load on the separating roller 86 is reduced, and as a result, the load current of the drive motor MOT1 is also reduced (L in FIG. 15). .

The load current of the drive motor MOT1 is a voltage value (Vi in FIG. 14) due to a voltage drop due to the detection resistor 65.
And is compared with the reference voltage VR by the voltage comparator 66. In the illustrated example, when the load current is large (Vi> VR), a signal of level "1" is input to the CPU, and when the load current is small (Vi <VR), "0" is input to the CPU. . The reference voltage VR is a preset value, and the voltage drop of the resistor 62 due to the MOT1 load current when the sheet exists between the separation roller 86 and the separation pad 87 is ViL, and when the sheet does not exist (the separation roller 86 And the separation pad 87 rubs directly), the voltage drop is ViH, and ViH>VR> ViL is set. Therefore, it can be determined whether the sheet has reached or has not reached the nip portion between the separation roller 86 and the separation pad 87 depending on whether the output of the voltage comparator 66 is “0” level or “1” level.

The CPU push-back means 1 (not shown) at the time when the output from the voltage comparator 66 reaches the "0" level or at a timing slightly after that.
0 is operated to push back the sheet on the pushing back means side. Therefore, only the first lowest sheet is fed. When the output from the voltage comparator 66 reaches the “0” level, the CPU turns off the solenoid 67 that drives the weight plate 83 (point c in FIG. 15) to release the pressing operation on the stacked sheets. . The separation roller 86 continues to rotate and conveys the lowest sheet.

Since the above-mentioned detecting means is based on the load fluctuation of the separating roller 86, it is not necessary to provide the sheet detecting means in the vicinity of the separating portion 85, and therefore the assembling property and the maintainability are not impaired. It is possible to detect the nip position of.

In the above embodiment, as a method of detecting the load of the paper feed motor MOT1, the separation roller 8 which is a paper feed roller is used.
Although the load current value of the DC motor driving 6 is detected, the rotation speed of the drive motor MOT1 may be detected from the rotation signal of the drive motor MOT1 from the encoder E. That is, when a DC motor is used as the drive motor and the voltage of the drive motor is controlled, when the sheet is nipped in the separation portion and the load of the drive motor becomes low, the motor rotation speed value increases. Therefore, it is possible to determine the time when the sheet is nipped in the separation portion by catching such a change at the rotational speed determined from the number of pulses per unit time of the encoder E.

[0058]

In summary, according to the present invention, the following excellent effects can be obtained.

(1) According to the first aspect of the invention, the second and subsequent sheets are also fed together with the feeding of the first sheet, and the sheet is fed between the feeding means and the reverse means. Even when nipped, the sheet on the reverse means side is pushed back by the reverse means in the direction opposite to the feeding direction, and only the sheet on the feeding means side is fed out in the forward direction. As a result,
Even if it is a sheet with strong adhesion such as an OHP sheet, a sheet that is strongly adsorbed by static electricity or a sheet with a high coefficient of friction that has been copied once, complete sheet separation is performed for each sheet and each sheet is reliably fed. It can be paper. Therefore, when it is used as a sheet feeding device of a copying machine, for example, it is free from the conventional manual feeding work of an OHP sheet or the like.

(2) According to the second aspect of the invention, when the leading edge of the sheet passes the position where the sheet is nipped by the conveying means and the reverse means, the second and subsequent sheets that are passing are pushed back by the pushing-back means. Is the same as that of claim 1, but since the push-back means is operated in conjunction with the descending operation of the sheet mounting table, it is pushed down by the push-back means. Therefore, a large air layer portion is formed between the first sheet and the second and subsequent sheets, and the separation between the first sheet and the second and subsequent sheets becomes more complete.

(3) Further, according to the inventions of claims 3 and 4, the paddle and the rotation preventing / rotating block structure of the rotary type are easy.
It is possible to obtain a simple structure in which the release is interlocked with the vertical movement of the sheet mounting table. Further, according to the fifth and sixth aspects of the present invention, by using the separate reverse roller and a separate shaft, it is possible to correspond to any other configuration.

[Brief description of drawings]

FIG. 1 is a sectional view showing a sheet feeding device according to an embodiment of the present invention.

2 is a development view showing a drive system of the sheet feeding apparatus of FIG. 1. FIG.

FIG. 3 is a diagram for explaining the operation of the sheet feeding apparatus of FIG.

FIG. 4 is a diagram for explaining the operation of the sheet feeding apparatus of FIG.

FIG. 5 is a diagram for explaining the operation of the sheet feeding device of FIG.

FIG. 6 is a diagram for explaining the operation of the sheet feeding apparatus of FIG.

FIG. 7 is a flowchart for explaining the control operation of the sheet feeding apparatus of FIG.

FIG. 8 is a diagram for explaining an action area of a paddle.

FIG. 9 is a diagram showing another configuration of the paddle.

FIG. 10 is a partial top view showing another configuration example of the paddle.

FIG. 11 is a side view showing another configuration example of the paddle.

FIG. 12 is a side view showing still another configuration example of the paddle.

FIG. 13 is a partial vertical sectional view of an automatic document feeder according to an embodiment of the present invention.

FIG. 14 is a configuration diagram of a control device of a drive motor MOT1.

FIG. 15 is a time chart diagram showing an operation of nip position detection.

[Explanation of symbols]

 1 OHP Sheet Feeding Cassette 2 Conveying Support Plate 2A Opening 2B Notch 3 Recess 4 Sheet Placement Table 4a Rotating Shaft 5 Lever 6 Lifting Drive Lever 7 Kick Roller 8 Separation Conveying Roller 8a Separation Conveying Roller 9 Separation Reverse Roller 9a Separation Reverse Roller shaft 10 Paddle 11 Paddle body 12 Locking part 13 Spring type torque limiter 14 Paddle lock claw 15 Tip claw part 16 Shaft 17 Spring 18, 19 Machine frame 20 Drive motor 21 Belt 22 Main gear 23, 25, 27, 28, 30 , 32, 34 Gear 24 Torque limiter 26, 29 Clutch 31, 33 Intermediate gear 35 Empty detection sensor (empty sensor) 36 Sheet leading edge detection sensor 37 Main body pickup roller 38 Air layer portion 40 Sheet bundle 40a Top sheet 55 Arc segment 56 Notch Flat part 7 Support Shaft 58 Swing Lever 58a Swing Center Shaft 59 Tip Curved Surface 60 Electromagnetic Solenoid 61 Load Detecting Means 62 Pushing Drive Means 63 Controller 64 Transistor 65 Detection Resistor 66 Voltage Comparator 67 Electromagnetic Solenoid 68 Drive Transistor 70 Automatic document feeder 71 Paper feed tray 80 Paper feed section 81 Pickup roller 82 Empty sensor 83 Weight plate (leaf spring) 84 Stopper 85 Separation section 86 Separation roller 87 Separation pad 88 Pad holder 89 Holding spring 93 Inversion space section 95 Registration roller C Electronic copying machine P Platen P1 Exposure reference position MOT1 Drive motor

Claims (6)

[Claims] 1. A feeding means for feeding a sheet stacked on a mounting table, and a reverse means provided opposite to the feeding means for giving a conveying force to the fed sheet in a direction opposite to a feeding direction. And a push-back means for applying a push-back force to the sheet on the reverse means side in a direction opposite to the feed direction after the leading edge of the sheet has passed a position where it is nipped by the feed means and the reverse means. A sheet feeding device characterized by: 2. A sheet placing table on which stacked sheets are placed and moved up and down, feeding means for feeding the sheet in contact with the sheet when the sheet placing table is raised, and a feeding means provided on the downstream side of the feeding means. Conveying means for conveying a sheet to be conveyed, a reverse means provided opposite to the conveying means for giving a conveying force in a direction opposite to the sheet feeding direction, and a push-back for applying a pushing-back force to the sheet on the reverse means side. A sheet feeding device, which is provided with a means and an interlocking means for operating the pushing back means together with the lowering operation of the sheet mounting table after the sheet has passed the position where the leading edge of the sheet is nipped by the conveying means and the reverse means. . 3. The sheet feeding device according to claim 1, wherein the pushing-back means is a rotary paddle provided on the same shaft as the separating reverse roller via a torque limiter. 4. A paddle lock claw for preventing rotation of the rotary paddle, and blocking and release of paddle rotation by the paddle lock claw are interlocked with vertical movement of the sheet mounting table. 3. The sheet feeding device according to item 3. 5. The sheet feeding apparatus according to claim 1, wherein the pushing-back means is a rotary paddle provided on a separate shaft from the separating reverse roller. 6. The sheet feeding apparatus according to claim 1, wherein the pushing-back means is a swing lever provided on a separate shaft from the separating reverse roller.