US20070001374A1

US20070001374A1 - Paper feeding device and an electronic apparatus having the same

Info

Publication number: US20070001374A1
Application number: US11/357,098
Authority: US
Inventors: Seung-jae Lee
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2005-06-13
Filing date: 2006-02-21
Publication date: 2007-01-04

Abstract

A paper feeding device and an electronic apparatus having the same include a pickup roller moving upwardly and downwardly to selectively contact a document stacked on a document tray. A restrainer moves in directions for blocking a leading end of a document stacked on the document tray from the feeding roller when the pickup roller is lifted, and for unblocking the leading end of document from the feeding roller when the pickup roller is lowered. Accordingly, unintended contact between the document and the feeding roller is prevented when stacking the document, thereby preventing damage of the document during paper feeding.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application the claims benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 2005-50305, filed Jun. 13, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an electronic apparatus. More particularly, the present invention relates to a paper feeding device supplying paper sheets into a main body of an electronic apparatus, and an electronic apparatus having the same.
2. Description of the Related Art
Generally, office electronic apparatuses, such as a photocopier, a scanner, a multifunction apparatus, and a printer, include a paper feeding device to supply a main body thereof with document sheets for recording thereon an image or document sheets bearing the image to be scanned. Recently, an automatic document feeder (ADF) has been developed and used, that is mounted on the outside of a main body of the electronic apparatus to automatically supply a plurality of document sheets one by one.
FIG. 1 schematically shows a conventional paper feeding device used in an office electronic apparatus. Referring to FIG. 1, a paper feeding device 10 includes a pickup roller 30 picking up document M stacked on a document tray 15. A feeding roller 20 feeds the document M picked up by the pickup roller 30 into the main body of the electronic apparatus. A friction member 40 is mounted corresponding to the feeding roller 20 to prevent the feeding of multiple sheets at one time into the main body.
In the conventional paper feeding device 10, when feeding the document M, the pickup roller 30 is lowered and brought into contact with the document M to feed the document M to the feeding roller 20. The feeding roller 20 then transfers the document M fed by the pickup roller 30 into the main body of the electronic apparatus. When the paper feeding operation is completed, the pickup roller 30 is lifted back to an initial position. The conventional paper feeding device 10 as described above is convenient since it can feed many sheets of document M into the main body sheet by sheet.
However, according to the conventional paper feeding device 10, when the document M is put nearer the feeding roller 20 rather than a preset correct position P, a leading end of the document M may contact with the feeding roller 20 even before the paper feeding. When the feeding roller 20 is rotated in this state, multiple-sheet feeding may be caused. The multiple-sheet feeding refers to an occurrence where a plurality of document sheets are overlappedly fed at once. Additionally, when many sheets of document M are stacked incorrectly as described above, the document M stacked at an upper part may be bent and damaged by contact with the feeding roller 20, as shown in FIG. 1. Furthermore, paper jams may be generated so that the document M cannot be advanced into the main body of the electronic apparatus. Thus, when the conventional paper feeding device 10 cannot assure normal operation of paper feeding, printing and scanning of an image may not be correctly performed.
Accordingly, a need exists for an improved paper feeding device for an electronic apparatus that substantially prevents feeding multiple sheets at one time.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the present invention is to provide an improved paper feeding device capable of assuring normal operation of paper feeding, and an electronic apparatus having the same.
A paper feeding device and an electronic apparatus having the same include a restrainer moving in directions for blocking a leading end of a document stacked on the document tray from the feeding roller when the pickup roller is lifted, and for opening a pathway between the leading end of the document from the feeding roller when the pickup roller is lowered.
According to another aspect of the present invention, paper feeding device and an electronic apparatus having the same include a paper feeding device for an electronic apparatus. A feeding roller is rotatable in a first direction for feeding a document picked up and fed from a document tray by a pickup roller into a main body of the electronic apparatus. A restrainer is movably disposed between the pickup roller and the feeding roller to open between the pickup roller and the feeding roller only when the feeding roller is rotated in the first direction.
Therefore, unintended contact between the document and the feeding roller may be substantially prevented, thereby preventing damage of the document during paper feeding.
According to an exemplary implementation of the present invention, the paper feeding device may further include a lifting and lowering driver that lowers the restrainer when the pickup roller is lifted and that lifts the restrainer when the pickup roller is lowered.
According to an exemplary implementation of the present invention, the pickup roller is connected to a driving source provided to the electronic apparatus through a predetermined gear train. The lifting and lowering driver includes a pinion mounted at the gear train. A rack gear part is formed at one side of the restrainer along an ascending and descending direction of the restrainer and meshed with the pinion.
According to an exemplary implementation of the present invention, the pinion is coaxially arranged with one selected from a plurality of idler gears mounted to the gear train. The lifting and lowering driver further includes a clutch for connection between the pinion and rotary shaft of the selected idler gear for selective power transmission.
According to an exemplary implementation of the present invention, the pinion is connected with one of the idler gears, which is rotated in the same direction with the pickup roller.
According to an exemplary implementation of the present invention, the pickup unit may include a feeding roller disposed between the driving source and the pickup roller to feed the document fed by the pickup roller into the main body of the electronic apparatus. The idler gear connected to the pinion is one of the plurality of idler gears connecting the feeding roller and the pickup roller to each other.
According to an exemplary implementation of the present invention, the pickup unit may include a frame supporting the idler gears and the pickup roller to be rotatable, and pivoted with respect to the feeding roller when the feeding roller is rotated. The frame includes a guide groove to contactingly support sliding of the side of the restrainer.
According to an exemplary implementation of the present invention, the clutch includes a spring clutch that rotates the pinion when the idler gears are rotated in a direction for lifting the restrainer and releases the connection between the idler gears and the pinion when the idler gears are rotated in a direction for lowering the restrainer, so that the restrainer descends by its own weight. According to this, power transmission by the idler gears and the pinion may be implemented with a simple structure and at a low cost.
According to an exemplary implementation of the present invention, the restrainer includes a contacting portion for contact with the frame at a predetermined position when being lifted by rotation of the pinion.
According to an exemplary implementation of the present invention, the paper feeding device may further include a detecting sensor detecting the document as fed to a predetermined position by the feeding roller. The feeding roller is driven in the opposite direction to a direction of feeding the document into the main body, thereby lifting the pickup roller and lowering the restrainer.
According to an exemplary implementation of the present invention, the restrainer includes a stopper restraining the leading end of document from advancing to the feeding roller while the restrainer is lowered. A guide part is connected to one side of the stopper and faces an upper side of the document being fed to the feeding roller while the restrainer is lifted.
According to an exemplary implementation of the present invention, the paper feeding device further includes a friction member mounted to face the feeding roller to substantially prevent multi-sheet feeding by friction with the document. The guide part is slanted with respect to the stopper to form an angle for guiding the document between the friction member and the feeding roller.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The above aspect and other features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawing figures, wherein;
FIG. 1 is a view of a conventional paper feeding device;
FIG. 2 is a schematic view of an image scanning apparatus employing the paper feeding device according to an exemplary embodiment of the present invention;
FIG. 3 is a perspective view of a pickup unit of FIG. 2; and
FIGS. 4 and 5 are schematic views illustrating the operation of the pickup unit according to an exemplary embodiment of the present invention.
Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, certain exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawing figures.
The matters defined in the description, such as a detailed construction and elements thereof, are provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the present invention may be carried out without those defined matters. Also, well-known functions or constructions are not described in detail to provide a clear and concise description of the exemplary embodiments.
FIG. 2 shows an image scanning apparatus as an example of electric apparatuses including a paper feeding device according to an exemplary embodiment of the present invention.
Referring to FIG. 2, an image scanning apparatus 100 according to an exemplary embodiment of the present invention includes a paper feeding device 200, an image sensor S, and a paper feeding path 130 connecting the paper feeding device 200 and the image sensor S.
The paper feeding device 200 includes a document tray 210 and a pickup unit 300 to supply a document M to the image sensor S. The document tray 210 is capable of stacking a plurality of sheets of document M thereon and exposed outside of the image scanning apparatus 100. A detection sensor SI detects whether the document M is stacked on the document tray 210.
The pickup unit 300 feeds the document M stacked on the document tray 210 sheet by sheet to the image sensor S while driving a pickup roller 330, and restrains the stacked document M from contacting with a feeding roller 320 during a standby mode. For this, as shown in FIGS. 2 and 3, the pickup unit 300 includes a feeding roller 320, the pickup roller 330, a restrainer 400, and a lifting and lowering driver 360.
The pickup roller 330 feeds the document M stacked on the document tray 210 to the feeding roller 320. The feeding roller 320 feeds the document M fed by the pickup roller 330 to the paper feeding path 130. The feeding roller 320 may be rotated by a predetermined driving source provided in a main body 110 of the electronic apparatus. As shown in FIG. 3, the pickup roller 330 according to an exemplary embodiment of the present invention is transmitted with a rotational force from the feeding roller 320 through a gear train 350 including a plurality of idler gears 351, 352, and 354 that are rotatably mounted on a frame 310. The gear train 350 is provided to transmit the rotational force from the feeding roller 320 to the pickup roller 330, which is at a predetermined distance from the feeding roller 320. To rotate the pickup roller 330 and the feeding roller 320 in the same direction, the gear train 350 includes an odd number of idler gears. In this exemplary embodiment, therefore, the gear train 350 has first to third idler gears 351, 352 and 354, as shown in FIG. 3. The frame 310 is connected to a feeding roller rotary shaft 321 to lift and lower the pickup roller 330 in association with rotation of the feeding roller 320. According to this structure, when the feeding roller 320 is rotated in a first direction B (FIG. 4) for feeding the document M, the pickup roller 330 is lowered in a direction D (FIG. 4) for contacting an upper side of the document M. When the feeding roller 320 is rotated in a second direction C (FIG. 5), that is opposite to the previous direction B, the pickup roller 330 is distanced from the document M in a direction E (FIG. 5). The pickup unit 300 may be configured as a single module including the feeding roller 320, the pickup roller 330, the idler gears 351, 352, and 354, the restrainer 400, and the lifting and lowering driver 360 that will be described hereinafter. As long as the feeding roller rotary shaft 321 of the feeding roller 320 is supportedly mounted in the main body 110, the other rollers and gears may be normally operated. Therefore, the assembling process of the main body 110 may be simplified by configuring the pickup unit 300 as a single module.
The restrainer 400 prevents contact between the leading end of the document M and the feeding roller 320 caused by stacking the document M carelessly in a standby mode in which the pickup roller 330 is lifted. The restrainer 400 is mounted to the pickup unit 300 to move up and down and has a stopper 410 and a guide part 420. The stopper 410 descends when the pickup roller 330 is lifted and thereby blocks between the feeding roller 320 and the leading end of the document M, as shown in FIG. 4. The guide part 420 extends from one side of the stopper 410. Ascending as the pickup roller 330 is lowered, the guide part 420 guides the upper side of the document M picked up by the pickup roller 330 between the feeding roller 320 and a friction member 290, as shown in FIG. 5. The friction member 290 is provided to substantially prevent multi-sheet feeding. The stopper 410 and the guide part 420 are, for example, slanted with respect to each other. Referring to FIG. 5, an angle θ formed between the stopper 410 and the guide part 420 has, for example, a size such that an end 420 a (FIG. 3) of the guide part 420 directs documents M between the friction member 290 and the feeding roller 320. The angle θ may be determined, for example, in consideration of varied positions of the restrainer 400 according to the descending of the pickup roller 330.
The restrainer 400 is moved up and down by the lifting and lowering driver 360 operated in association with rotation of the feeding roller 320. In this exemplary embodiment, the lifting and lowering driver 360 includes a pinion 361 and a rack gear part 365. The pinion 361 is rotatably supported by the frame 310 to be coaxially arranged with the second idler gear 352 for driving the pinion 361. In an exemplary implementation, the second idler gear 352 is rotated in the same direction as the pickup roller 330. The rack gear part 365 is formed at one side of the restrainer 400 facing the pinion 361 along an ascending and descending direction of the restrainer 400, and engages with the pinion 361. As shown in FIG. 3, a pinion rotary shaft 362 of the pinion 361 and an idler gear rotary shaft 353 of the second idler gear 352 are connected to each other through a spring clutch 367. Accordingly, when the feeding roller 320 is rotated in the first direction B (FIG. 4), the spring clutch 367 is compressed and therefore, the pinion 361 is rotated in association with driving of the second idler gears 352. Consequently, the restrainer 400 is lifted. The restrainer 400 is lifted until a contacting portion 411 thereof is brought into contact with the frame 310. In this exemplary embodiment, the restrainer 400 is lifted until the contacting portion 411 is stopped by an end of a guide groove 315 formed on an inner wall of the frame 310. However, the present invention may be embodied in other various ways. For example, the restrainer 400 may be in another form so that lifting of the restrainer 400 may be restricted by contact thereof with a lower end of the frame 310. Furthermore, another type of clutch may be used instead of the spring clutch 367 to connect the respective second idler gears 352 with the pinion 361 for selective power transmission. The guide groove 315 is formed on an inner wall of the frame 310 for sliding of a side edge of the restrainer 400, so that the restrainer 400 may be lifted with the rack gear part 365 and the pinion 361 firmly meshed with each other. When the feeding roller 320 is stopped or rotated in the second direction C (FIG. 5), the restrainer 400 descends by its own weight since the pinion 361 driven by the spring clutch 367 is stopped. The restrainer 400 descends until a lower end of the stopper 410 contacts a bottom surface 210 a of the document tray 210, which supports a lower side of the document M, as shown in FIG. 4.
An exemplary embodiment of the present invention applied to the image scanning apparatus has been described so far. However, the present invention is not limited to this case but applicable for other various office electronic apparatuses requiring paper supply, such as a printer, a copier, and a facsimile.
The operation of the paper feeding device according to an exemplary embodiment of the present invention will now be described with reference to FIGS. 4 and 5.
In the standby mode in which the document M is not being fed, the restrainer 400 is in a lowered state, as shown in FIG. 4. Therefore, when stacking the sheets of document M, contact between the leading end of the document M and the feeding roller 320 is prevented. When the feeding roller 320 starts rotating in the first direction B to feed the document M, the pickup roller 330 is lowered in the arrowed direction D (FIG. 4) and contacts the upper side of the document M, as shown in FIG. 5. When the pickup roller 330 is lowered, the restrainer 400 is lifted in an arrowed direction F (FIG. 4) by reciprocal action of the rack gear 365 and the pinion 361 until an end of the guide part 420 directs sheets of document M between the feeding roller 320 and the friction member 290. After the restrainer 400 is lifted and the pickup roller is lowered completely, the pickup roller 330 is rotated in the first direction B and feeds an uppermost sheet of the document M stacked on the document tray 210 to the feeding roller 320. The upper side of the document M being fed by the pickup roller 330 is prevented by the guide part 420 of the restrainer 400 from being lifted over a predetermined height. The document M fed to the feeding roller 320 is fed to the paper feeding path 130 (FIG. 2) by rotation of the feeding roller 320. The feeding roller 320 is rotated until the detection sensor S2 (FIG. 2) senses the document M having been fed to a predetermined position.
When the paper feeding by the feeding roller 320 is completed, the feeding roller 320 is rotated in the second direction C to lift the pickup roller 330 in an arrowed direction E (FIG. 5) so that the pickup roller 330 is separated from the document M. At this time, as a driving force of the second idler gear 352 applied to the pinion 361 is removed, the restrainer 400 descends by its own weight in an arrowed direction G After the restrainer 400 is lowered and the pickup roller 330 is lifted completely, the respective parts are positioned as shown in FIG. 4 and stand by in this state until feeding of another document M is required.
According to an exemplary embodiment of the present invention as described above, contact of the document M stacked on the document tray 201 with the feeding roller 320 is restricted when the feeding roller 320 and the pickup roller 330 are not driven. According to this configuration, unintended contact between the document M and the feeding roller 320 while the document M is stacked on the document tray 201 may be prevented, thereby restraining damage of the document M by the feeding roller 320 being rotated for the paper feeding. Additionally, the upper side of the document M may be controlled by the guide member 420 when the restrainer 400 is lifted, thereby restraining damage of the document M by rotation of the feeding roller 320, which is caused when the document M is incorrectly fed. Finally, deterioration of quality of printed image and read image may be prevented.
While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A paper feeding device for an electronic apparatus, comprising:

a pickup roller moving upwardly and downwardly to selectively contact a document stacked on a document tray and to feed the contacted document; and

a restrainer moving between a first position that blocks a leading end of the document stacked on the document tray from the feeding roller when the pickup roller is lifted and a second position that unblocks the leading end of the document from the feeding roller when the pickup roller is lowered.

2. The paper feeding device of claim 1, wherein the restrainer includes

a stopper restraining the leading end of the document from entering a main body of the electronic apparatus while the restrainer is lowered; and

a guide part connected to one side of the stopper and facing an upper side of the document being fed to the feeding roller while the restrainer is lifted.

3. The paper feeding device of claim 2, wherein

a lifting and lowering driver lowers the restrainer when the pickup roller is lifted and lifts the restrainer when the pickup roller is lowered.

4. The paper feeding device of claim 3, wherein

the pickup roller is connected to a driving source disposed in the electronic apparatus through a predetermined gear train, and

the lifting and lowering driver includes a pinion mounted at the gear train, and a rack gear part formed at one side of the restrainer along an ascending and descending direction of the restrainer that engages the pinion.

5. The paper feeding device of claim 4, wherein

the pinion is coaxially arranged with one idler gear selected from a plurality of idler gears mounted to the gear train, and

the lifting and lowering driver includes a clutch disposed between the pinion and rotary shaft of the selected idler gear for selective power transmission.

6. The paper feeding device of claim 5, wherein

the selected idler gear connected with the pinion is rotated in the same direction with the pickup roller.

7. The paper feeding device of claim 6, wherein

the feeding roller is disposed between the driving source and the pickup roller to feed the document fed by the pickup roller into the main body of the electronic apparatus, and

the selected idler gear is one of the plurality of idler gears connecting the feeding roller and the pickup roller to each other.

8. The paper feeding device of claim 7, wherein

a frame rotatably supports the idler gears and the pickup roller, and pivots with respect to the feeding roller when the feeding roller is rotated; and

the frame has a guide groove that slidably receives a side of the restrainer.

9. The paper feeding device of claim 8, wherein

the clutch includes a spring clutch that rotates the pinion when the selected idler gear is rotated in a direction for lifting the restrainer and releases the connection between the selected idler gear and the pinion when the selected idler gear is rotated in a direction for lowering the restrainer, so that the restrainer descends by its own weight, and

the restrainer has a contacting portion that contacts the frame at a predetermined position when being lifted by rotation of the pinion.

10. The paper feeding device of claim 7, wherein

a detecting sensor detects the document as fed to a predetermined position by the feeding roller, and

the feeding roller is driven in the opposite direction to a direction of feeding the document into the main body when the detecting sensor detects the document, thereby lifting the pickup roller and lowering the restrainer.

11. The paper feeding device of claim 2, wherein

a friction member is mounted to face the feeding roller to substantially prevent multi-sheet feeding by creating friction with the fed document; and

the guide part is slanted with respect to the stopper to form an angle for guiding the document between the friction member and the feeding roller.

12. An electronic apparatus, comprising:

a pickup roller picking up a document stacked on a document tray;

a feeding roller feeding the document picked by the pickup roller to an image sensor; and

a restrainer moving between a first position for blocking a leading end of the document from the feeding roller when the pickup roller is lifted, and a second position for unblocking the leading end of the document from the feeding roller when the pickup roller is lowered.

13. The electronic apparatus of claim 12, wherein the restrainer includes

a stopper restrains the leading end of the document from advancing to the feeding roller while the restrainer is lowered; and

14. The electronic apparatus of claim 13, wherein

the guide part is slanted with respect to the stopper to face an upper side of the document being fed by the pickup roller to the feeding roller when the restrainer is lifted.

15. The electronic apparatus of claim 13, wherein

16. The electronic apparatus of claim 15, wherein

the pickup roller is connected to the feeding roller through a plurality of idler gears to be rotated in association with rotation of the feeding roller, and

the lifting and lowering driver includes a pinion connected with one idler gear selected from the plurality of idler gears, and a rack gear part formed at one side of the restrainer along an ascending and descending direction of the restrainer and that engages the pinion.

17. The electronic apparatus of claim 16, wherein

the lifting and lowering driver includes a clutch disposed between the pinion and a rotary shaft of the selected idler gear for selective power transmission, and

the clutch rotates the pinion when the selected idler gear is rotated in a direction that separates the restrainer from the document.

18. The electronic apparatus of claim 16, wherein

a frame rotatably supports the idler gears and the pickup roller and pivots so that the pickup roller is selectively contacted with the document according to rotation of the feeding roller; and

the selected idler gear connected to the pinion is pivoted in a direction for lifting the restrainer when the pickup roller is lowered.

19. The electronic apparatus of claim 18, wherein

the frame rotatably supports the feeding roller and movably supports the restrainer; and

the pickup roller, the idler gears, the restrainer, the lifting and lowering driver, the feeding roller, and the frame are formed as a single module that is mounted to a main body of the electronic apparatus.

20. The electronic apparatus of claim 16, wherein

the pinion is coaxially connected with the selected idler gear, which is rotated in the same direction as the pickup roller; and

the clutch is a spring clutch including a spring connecting the pinion with a rotary shafts of the selected idler gear.

21. A paper feeding device for an electronic apparatus, comprising:

a feeding roller rotatable in a first direction for feeding a document picked up and fed from a document tray by a pickup roller into a main body of the electronic apparatus; and

a restrainer movably disposed between the pickup roller and the feeding roller to open a pathway between the pickup roller and the feeding roller only when the feeding roller is rotated in the first direction.

22. The paper feeding device of claim 21, wherein

a lifting and lowering driver lifts and lowers the restrainer in association with the feeding roller.

23. The paper feeding device of claim 22, wherein the restrainer includes

a stopper blocking the document pathway between the pickup roller and the feeding roller when the restrainer is lowered; and

a guide part slantingly connected to one side of the stopper and facing an upper side of the document being fed to the feeding roller when the restrainer is lifted.

24. The paper feeding device of claim 23, wherein the lifting and lowering driver includes

a pinion connected with one idler gear selected from a plurality of idler gears that power-transmittably connect the feeding roller and the pickup roller; and

a rack gear part formed at one side of the restrainer along an ascending and descending direction of the restrainer and that engages the pinion.

25. The paper feeding device of claim 24, wherein

the lifting and lowering driver includes a clutch connecting the pinion with the selected idler gear for selective power transmission.

26. The paper feeding device of claim 24, wherein

the pinion and the selected idler gear are coaxially arranged with each other, and

the clutch is a spring clutch connecting a rotary shaft of the pinion and a rotary shaft of the selected idler gear.

27. The paper feeding device of claim 23, wherein

the feeding roller is rotated in a second direction opposite to the first direction after completing document feeding by rotating in the first direction, and

the pickup roller is lowered to contact the document when the feeding roller is rotated in the first direction and is lifted in to be separated from the document when the feeding roller is rotated in the second direction.

28. The paper feeding device of claim 27, wherein

the restrainer is lifted as the feeding roller is rotated in the first direction to open the document pathway between the feeding roller and the pickup roller, and is lowered as the feeding roller is rotated in the second direction to block the document pathway between the feeding roller and the pickup roller.

29. The paper feeding device of claim 23, wherein

the restrainer is lifted as the feeding roller is rotated in the first direction to open the document pathway between the feeding roller and the pickup roller, and is lowered as the feeding roller is not driven to block the document pathway between the feeding roller and the pickup roller.

30. The paper feeding device of claim 29, wherein

the restrainer is lowered by its own weight after the document feeding is completed.