JPH05147831A - Paper feeding device - Google Patents

Abstract

PURPOSE:To surely feed a paper sheet separately one at a time and to prevent the paper sheet from being stained by toner at the time of separating operation. CONSTITUTION:After a separated lowermost paper sheet is detected by a paper detecting sensor 215, a paper sheet returning claw 300 is moved from a retreating position to a separation nip part side to start push back operation for pushing back a paper sheet staying in the separation nip part.

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 applied to an image forming apparatus such as a copying machine, facsimile machine, printer or the like, and more particularly, to a sheet bundle on which an image has already been formed on one side by friction separation. And a paper feeding device such as an automatic double-sided paper feeding device.

[0002]

2. Description of the Related Art In a sheet feeding device that feeds sheets one by one from a bottom sheet side of a sheet bundle having an image formed on one side by friction, a sheet feeding / separating section is provided with a feeding roller and a separating roller. A roller pair or a feeding belt and a separating roller that is pressed against the belt. Generally, when the leading edge of the paper enters the separation nip portion and separation is performed by frictional force, the paper surface that separates and advances at the nip portion is
It is strongly rubbed by the leading edge of the next sheet that is retained. In particular, when feeding a stack of sheets with the image side facing upward from the bottom sheet, the image surface of the sheet that separates and advances is rubbed and the toner falls off, and the dropped toner is the back side of the next sheet. Since the paper is concentrated and accumulated at the leading edge, the leading edge of the sheet easily becomes dirty. Contamination at the leading end of the paper is related to the fixability of the toner, but since the fixability is generally poor on thick paper and the like, such pollution is likely to occur and the copy finish is deteriorated. Also, when the separation roller is rotated in the reverse direction of the paper through the torque limiter, when the separation roller is separated, the leading edge of the stationary paper is rolled up along the surface of the separation roller and the leading edge of the paper is broken, When the paper is fed, it is easy for the paper not to be fed. In view of such a problem, for example, in Japanese Patent Publication No. 3-6101, double feed preventing means is provided so as to be press-contactable with and away from the friction conveying means, and after separating the first sheet, There is disclosed an automatic sheet feeding device provided with a movable sheet stop member that prevents the second sheet from advancing.

[0003]

In the above-mentioned prior art, since the separating roller is separated from the feed belt after separating the bottom sheet, a large number of sheets are separated at a time when the next sheet is fed. It has a drawback that it is easy to get in, and the paper is likely to be double-fed. Further, since the paper stop member exerts the paper stopping function when the separated paper reaches the next roller, the paper is not soiled at the portion corresponding to the distance from the separation nip portion to the next roller. I can't avoid it. The present invention has been made based on such a background, and it is possible to reliably separate and feed the sheets one by one, and to prevent the sheets from being contaminated by toner during the separating operation as much as possible. An object of the present invention is to provide a sheet feeding device that can perform the above.

[0004]

The object is to feed a lowermost sheet of a bundle of a plurality of sheets having an image formed on at least one side thereof, and to face the feed roller and rotate in the same direction, The multi-feed preventing roller that separates and feeds the sheets one by one by frictional force, and the separated sheet that is moved from the retreat position downstream of the separation nip portion of the feed roller and the multi-feed preventing roller In this regard, the leading end portion is inserted between the sheets retained at the separation nip portion and the sheet returning means for pushing the retained sheet back to the upstream side of the separation nip portion, and the sheet separated at the downstream side of the separation nip portion. It is achieved by having a paper detecting means for detecting the leading edge of the sheet, and starting the pushing back operation of the stopped paper by the paper returning means after the separated bottom paper is detected by the paper detecting means. That.

[0005]

When the lowermost sheet separated by the double feed prevention roller is detected by the sheet detecting means, the sheet returning means moves from the retracted position to move the retained sheet to the upstream side of the separation nip portion. Push back Push back operation is started.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a double-sided copy sheet conveying system of a copying machine. The sheet 2 fed from the A direction, the image is transferred from the photosensitive drum 1, and the image-formed sheet 2 on one side passes through the fixing device 3,
The toner image is fixed, the conveyance path is changed from the B direction to the C direction by the branching claw 4, and the double-sided device 10 is passed through the conveyance roller pair 5.
It is sent into 0. The direction of the leading edge of the sheet 2 is reversed by about 180 degrees by the rotation of the deflection rotator 105 having the clamp claws, while the rear portion of the sheet 2 is advanced in the sheet discharge direction by the transport belt 6 that is in contact with it. Since the leading edge of the sheet 2 is stopped at the reverse position, the sheet 2 is formed while forming a curved surface that advances between the transport belt 6 and the intermediate tray 7.
When the trailing edge of the sheet advances and the trailing edge of the sheet comes out of contact with the transport belt 6, the sheet is sequentially stacked on the intermediate tray 7 due to its own weight. At this time, the alignment process in the paper width direction is performed by the jig yoga 130. Note that the image surface of the sheet 2 faces upward in this state. When a predetermined number of sheets have been loaded,
The moving plate 13 moves in the E direction by a predetermined distance, and moves the two stacked sheets of paper to the refeed position. In the figure, 14 is a drive wire, 15 is a stepping motor for driving the drive wire 14, and 28 is a home position sensor of the moving plate 13.

FIG. 2 is a vertical sectional view of the re-feeding device of the double-sided device 100. At the lower right of the intermediate tray 7, a half-moon-shaped feed roller 8 whose outer periphery is partially cut off is arranged. The feed roller 8 contacts the bottom sheet of the two stacks of sheets on the intermediate tray 7. Ready to send. A pressure plate 201, which is supported by a support shaft 202 and swings around the support shaft 202, is provided above the feeding end of the two stacks of stacked sheets. The pressure plate 201 is normally retracted to the inside of the upper guide plate 205 as shown in the figure. However, at the time of feeding the paper, the pressure plate 201 is synchronized with the intermittent rotation of the feeding roller 8 from the feeding hole 205a provided in the upper guide plate 205. The two stacks of stacked sheets are dropped and come into contact with each other, and the leading edge of the two bundles of stacked sheets is urged toward the feed roller 8. The separation unit of the sheet re-feeding device presses the sheet re-feeding feed roller 9 that conveys the sheet 2 in the sheet feeding direction, and the sheet re-feeding feed roller 9 as a double-feeding prevention unit in the same direction as the sheet re-feeding feed roller 9 (the sheet is returned). Direction) Re-feed separation roller 1 driven to rotate
0, the return claw 300 for pushing back the sheet 2, the return claw 30
It includes a solenoid 350 that drives 0, a link mechanism that transmits a driving force, and the like. The coefficient of friction between the surfaces of the re-feeding feed roller 9 and the re-feeding separating roller 10 is μ ₁ , respectively.
If μ _{2 is} the friction coefficient between papers and μ _p , μ _p <μ ₂ <
Select the material of each roller so that it becomes μ ₁ .
Due to the difference in the friction coefficient, during the re-feeding operation, only one sheet of the lowermost sheet 2 is fed out from the separation nip portion, and the second sheet 2 thereon is prevented from advancing. ..

Downstream of the separating section, the upper guide plate 205 and the lower guide plate 206 form a conveying path for the sheet 2, and a sheet detecting sensor 215 and a pair of grip rollers 216 for conveying the sheet 2 are provided downstream of the separating nip section. Has been. The upstream side of the separation portion of the upper guide plate 205 is formed of a stepped guide surface having a surface parallel to the intermediate tray 7, and the lower stepped guide surface has an elastic friction sheet 207 supported to be inclined thereto.
Is provided. The lower end of the elastic friction sheet 207 is a free end that can be elastically deformed.
There is a gap d between the lower end of the sheet and the upper surface of the downstream side edge of the intermediate tray 7, through which a regulated number of sheets 2 can pass.
The return claw 300 is supported by the rotary shaft 301, and is connected to the stopper 30.
The movement to the downstream side is regulated by 6. The rotating shaft 301 is fixed to the stay 208. FIG. 7 is a perspective view showing the tip portion 300a of the return claw 300. As shown in the figure,
The tip of the tip portion 300a of the return claw 300 has a wedge shape deviated from the main surface of the paper contacting side, and a thin elastic sheet 300b (a polyester film having a thickness of 0.05 to 0.2 mm) is attached to the upper surface thereof. ing. Further, a cushioning sheet 300c made of felt (fluffing cloth) is attached to the front surface of the stem column of the tip portion 300a to reduce the impact when the paper 2 is abutted.

FIG. 3 is a schematic diagram of the re-feeding device in the paper feeding state, and FIG. 4 is a schematic diagram showing the movement of the return pawl during the paper feeding operation. FIG. 5 is a partial cross-sectional view showing the drive mechanism of the return pawl, and FIG. 6 is a cross-sectional view showing the drive mechanism of the re-feed separation roller. As shown in FIG. 5, a pair of return claws 300 </ b> A and 300 </ b> B sandwiching the sheet re-feed separation roller 10 is swingably supported around the support shaft 301. The driven arm 302 axially fixed to one end of the support shaft 301, the drive arm 303 one end of which is axially fixed to the protrusion of the stay 208, and the intermediate link 304 connecting the drive arm 303 and the driven arm 302 have a four-bar linkage mechanism. Constitute. The one end 351a of the lever 351 that is rotated by the protrusion of the operating rod of the solenoid 350 presses the side edge portion of the drive arm 303 or separates it from the side edge portion, so that the tip portion 300a of the return claw 300 is moved to the upper guide plate. The position S1 retracted to the inside of 205 and the position S2 projecting toward the separation nip portion are swung. When the one end 351a of the lever 351 is separated from the side edge portion of the drive arm 303, the return claw 300 is biased in the counterclockwise direction by the elastic force of the return spring 305 and is regulated by the stopper 306 and returned. The claw 300 stops at the retracted position S1. In FIG. 6, c is the paper 2
The center line of the conveyance direction of is shown.

The re-feed separation roller 10 is provided on a rotary shaft 225, and the rotary shaft 225 is integrated with a bearing portion 227 so as to be swingable in the direction of the re-feed feed roller 9. When the electromagnetic clutch (CL2) 251 is energized, the rotational driving force from the driving source is the gears 253, 254,
The rotation shaft 225 is rotated in the arrow direction in FIG. 6 by being transmitted in the order of 255 and 256. A spring 230 is provided between the re-feeding feed roller 9 and the re-feeding separating roller 10 to generate a pressing force to press each other. On the other hand, when the electromagnetic clutch 251 is de-energized, the one-way clutch bearing 228 provided on the fixed rotation shaft 226 prevents the re-feed separation roller 10 from rotating together with the sheet 2.

Next, the operation of the sheet refeeding apparatus will be described with reference to FIGS. 2, 3, and 4. In FIG. 2, two bundles of sheets are conveyed in the direction of the separation nip portion by the delivery roller 8, and the amount of passage of the sheets of paper 2 is regulated by the elastic friction sheet 207 during the conveyance, so that one of the lower layers of the two bundles of sheets is Only the copy 2 is sent first. At this time, in synchronization with the rotation of the feed roller 8, the pressure plate 201 descends onto the bundle of two sheets to assist the conveyance of the sheets 2. Further, at this time, since the electromagnetic clutch 251 is energized, the re-feed separation roller 10 as the double-feed preventing means is pressed against the re-feed feed roller 9 to rotate together. When a part of the lower layer of the two bundles of sheets is sent to the separating nip portion, the lowermost sheet 2 is separated and separated, and the sheet 2 is further advanced and conveyed to the grip roller pair 216. On the way, when the leading edge of the sheet 2 is detected by the sheet detection sensor 215, the solenoid 350 is energized, the driving force is transmitted through the link mechanism, and the return claw 300 is moved from the retracted position S1 to the advanced position S2. To move.

As shown in FIG. 4, the distance from the rotary shaft 301 to the tip portion 300a is set so that the trajectory drawn by the tip portion 300a is an arc having a radius R slightly exceeding the nip point. As the return pawl 300 moves, the leading end portion 300a slightly pushes down the sheet 2 being conveyed and advances from the ejection side to the entry side of the separation nip portion. At this time, the angle θ formed by the tangent line at the intersection of the loci drawn by the leading end portion 300a and the paper surface of the conveyed paper 2 is set to 5 to 30 °, so that as the return claw 300 moves to the advanced position S2. , The leading end portion 300a is inserted below the second sheet of paper 2 retained at the separation nip portion without damaging it, and grips these paper sheets 2 to a position slightly upstream of the separation nip portion. Can be pushed back. After the return claw 300 reaches the separation nip portion, after a predetermined delay time is detected by the timer, the electromagnetic clutch 251 is de-energized and the re-feed separation roller 10 is stopped. When the trailing edge of the sheet 2 is detected by the sheet detection sensor 215, the solenoid 350 is de-energized, and the return claw 300 returns to the retracted position S1. As described above, in the present embodiment, the non-stop paper is quickly discharged after the separating operation in the separation nip portion, so that the toner stain on the paper surface due to the friction between the non-stop paper and the paper 2 which is separated and conveyed can be prevented. Paper 2 between separation nip and grip roller pair 216
Is inevitable in principle, but in many cases,
Since this portion serves as a margin or a binding margin, there is often no problem in practical use.

In the present embodiment, the re-feeding feed roller 9 and the re-feeding separating roller 10 are arranged above and below the sheet conveying center line c, and the return claw 300 is arranged on the left and right so as to be symmetrical with respect to these separating means. Since it is installed in the
This is convenient because it can prevent slanted conveyance. Further, generally, since the leading edge of the sheet 2 has a bent portion or a wavy shape, the return claw 300 provided close to the separating means is as described above.
The first sheet 2 conveyed with the leading end portion 300a separated
The second sheet of paper 2 that has been stopped is scooped up by pushing down a little, so that double feeding of the paper 2 can be reliably prevented. The thin elastic sheet 300b of the tip portion 300a of the return claw 300 is not limited to the synthetic resin material and may be a metal material. Further, when the paper 2 is a thin letter or the like, the tip of the return pawl 300 is likely to be scratched or broken during the returning operation by the return pawl 300. Therefore, the pawl width of the return pawl 300 may be appropriately widened or pushed back by increasing the number thereof. The force may be dispersed. Further, as shown in FIG. 8, the re-feeding feed roller 9 and the re-feeding separation roller 10 do not come into pressure contact with each other,
The same effect of preventing double-feeding can be expected even if the two are arranged so as to face each other with a slight gap.

According to this embodiment, the following effects are obtained. (1) Since the re-feed separation roller 10 does not separate from the re-feed feed roller 9 after separating the bottom sheet of the two bundles of paper, a large number of sheets 2 are separated at a time when the next sheet 2 is fed. It is possible to prevent double feeding due to being sent to the section. (2) After the separating operation, the re-feed separating roller 10 rotates together to assist the conveyance of the separated sheet 2, so that the conveying force of the sheet 2 can be prevented from decreasing. (3) Since the paper detection sensor 215 is provided downstream of the separation nip portion to control the return claw 300 to return after the conveyed first sheet 2 is reliably separated, the paper is detected at the separation nip portion. 2 slips and the separating operation is delayed, and thus the returning operation of the returning claw 300 is delayed, and the contamination range can be prevented from expanding during that time. Therefore, the reliability of the returning operation is increased and the contamination range of the leading end of the paper 2 is increased. Can be further reduced.

[0015]

According to the first aspect of the invention, after the separated bottom sheet is detected by the sheet detecting means, the sheet returning means is moved from the retracted position to push back the stopped sheet. Since it is started, it is possible to prevent the toner stains on the sheets during the separating operation in the separating nip portion as much as possible, and reliably separate the sheets one by one and feed them.

According to the second aspect of the present invention, the sheet returning means is a hook-shaped member whose front end side is bent upstream.
Since at least one pair of the hook-shaped members are arranged at substantially symmetrical positions with the feed roller and the double-feed prevention roller sandwiched therebetween, the paper sheet retained in the separating portion is reliably gripped by the hook-shaped member and pushed back. At the same time, it is possible to prevent the inclined conveyance of the sheet.

According to the third aspect of the present invention, the thin sheet elastic body is provided on the upper surface of the leading end portion of the sheet returning means, and when the stopped sheet is pushed back, the thin sheet elastic member is attached to the lowermost sheet to be conveyed. Since the contact is made at an approach angle of -30 degrees and it is inserted between the stationary paper and the stationary paper, the reliability of the pushing back operation of the stationary paper by the paper returning means is improved, and the damage of the paper and the flaky elastic body is prevented. can do.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a double-sided copy sheet conveying system of a copying machine according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a re-feeding device of a double-sided device of a copying machine.

FIG. 3 is a schematic view of the re-feeding device in a paper feeding state.

FIG. 4 is a schematic diagram showing the movement of the return pawl during a paper feeding operation in the paper refeeding device.

FIG. 5 is a partial cross-sectional configuration diagram showing a drive mechanism of a return pawl.

FIG. 6 is a cross-sectional view showing a drive mechanism of a re-feed separation roller of the re-feed device.

FIG. 7 is a perspective view showing a tip portion of a return pawl.

FIG. 8 is a side view of a re-feeding feed roller and a re-feed separating roller according to a modified example of the embodiment of the present invention.

[Explanation of symbols]

 9 Refeed Feed Roller 10 Refeed Separation Roller 215 Paper Detection Sensor 216 Gripper Roller Pair 300 Return Claw 300b Flaky Elastic Sheet 350 Solenoid

Claims (3)

[Claims] 1. A friction roller is provided with a feed roller that conveys a bottom sheet of a bundle of a plurality of sheets having an image formed on at least one side thereof, and a double feed prevention roller that faces the feed roller and that rotates in the same direction. In the paper feeding device that separates and feeds the sheets one by one, the feed roller and the double feed prevention roller are separated from each other by moving from a retreat position retracted from a paper conveyance path downstream of the separation nip portion where the feed roller and the double feed prevention roller are in pressure contact with each other. A sheet and a sheet returning means for inserting the leading edge between the sheet retained on the separation nip portion and the sheet resting on the upstream side of the separation nip portion, and the separation nip. A sheet detecting means for detecting the leading edge of the separated sheet on the downstream side of the section, and after the leading edge of the separated bottom sheet is detected by the sheet detecting means, the sheet returning means stops the sheet. A paper feeding device characterized in that a push-back operation of paper is started. 2. The paper returning means according to claim 1, wherein the paper returning means is composed of a hook-shaped member whose front end side is bent to the upstream side, and the hook-shaped member is at least at a substantially symmetrical position with the feed roller and the double feed prevention roller interposed therebetween. A sheet feeding device, which is arranged in pairs. 3. The sheet returning means according to claim 1, wherein the sheet returning means has a thin piece-like elastic body on the upper surface of the tip portion thereof, and the thin piece-like elastic body is used for pushing back the retained sheet by the sheet returning means.
A sheet feeding device, which is brought into contact with a sheet to be separated and conveyed at an approach angle of 5 to 30 degrees and is inserted between the sheet and the stationary sheet.