US20100032891A1 - Sheet feeding device and image forming apparatus - Google Patents
Sheet feeding device and image forming apparatus Download PDFInfo
- Publication number
- US20100032891A1 US20100032891A1 US12/461,185 US46118509A US2010032891A1 US 20100032891 A1 US20100032891 A1 US 20100032891A1 US 46118509 A US46118509 A US 46118509A US 2010032891 A1 US2010032891 A1 US 2010032891A1
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- United States
- Prior art keywords
- sheet
- belt
- feeding device
- sheet feeding
- stack
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H3/00—Separating articles from piles
- B65H3/18—Separating articles from piles using electrostatic force
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H3/00—Separating articles from piles
- B65H3/02—Separating articles from piles using friction forces between articles and separator
- B65H3/04—Endless-belt separators
- B65H3/047—Endless-belt separators separating from the top of a pile
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H2515/00—Physical entities not provided for in groups B65H2511/00 or B65H2513/00
- B65H2515/70—Electrical or magnetic properties, e.g. electric power or current
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
- B65H2801/00—Application field
- B65H2801/03—Image reproduction devices
- B65H2801/06—Office-type machines, e.g. photocopiers
Definitions
- Illustrative embodiments described in this patent specification generally relate to a sheet feeding device to separate a stack of sheets and feed the sheets one by one, and an image forming apparatus including the sheet feeding device.
- Related-art image forming apparatuses such as copiers, facsimile machines, printers, or multifunction devices having two or more of copying, printing, scanning, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet) according to image data using an electrophotographic method.
- a recording medium e.g., a sheet
- a charger charges a surface of a latent image bearing member (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet.
- the sheet bearing the fixed toner image is then discharged from the image forming apparatus.
- the image forming apparatuses further include a sheet feeding device to feed recording media such as a sheet.
- a friction paper feed method using a pickup member is widely employed in the sheet feeding device.
- the pickup member include a roller and a belt each including a material having a larger coefficient of friction such as rubber.
- the pickup member needs to be pressed against the sheet using a spring or the like to obtain a larger fictional force. Because the coefficient of friction at the surface of the material having a larger coefficient of friction such as rubber is changed over time and by environmental factors, the friction paper feed method cannot stably provide a higher ability to reliably feed the sheet.
- a sheet feeding device including a seamless dielectric belt rotated in a direction of sheet feed.
- the seamless dielectric belt contacts a top surface of a stack of sheets, and alternating charges (that is, electrical charges of alternating polarity) are applied to a surface of the seamless dielectric belt by a member.
- the member includes a charging unit to form an alternating charge pattern on the surface of the seamless dielectric belt and a neutralizing unit to de-charge, or neutralize, the surface of the seamless dielectric belt.
- the charges thus applied to the surface of the seamless dielectric belt generate an electric field that in turn generates an attractive electrostatic force that attracts the sheet to the surface of the seamless dielectric belt.
- a sheet placed at the top of the stack of sheets hereinafter referred to as a top sheet
- a top sheet is separated from the rest of the stack of sheets and is conveyed in the direction of sheet feed.
- a separation/conveyance device that includes an attraction/separation unit to alternately attract and support a top sheet placed at the top of the stack of sheets using an attractive force generated by a non-uniform electric field and separate the top sheet from the stack of sheets.
- the separation/conveyance device further includes a drive control unit to move the attraction/separation unit, a sheet conveyance unit to convey the top sheet thus separated, and an auxiliary separation unit to assist the attraction/separation unit to separate the top sheet from the stack of sheets.
- the drive control unit moves the attraction/separation unit from a leading edge side of the top sheet to a predetermined position to contact the top sheet, and stops the attraction/separation unit at that position.
- the drive control unit moves the attraction/separation unit again.
- the auxiliary separation unit applies a predetermined force between the top sheet attracted to the attraction/separation unit and a second sheet, that is, a next sheet placed immediately beneath the top sheet, to separate the top sheet from the second sheet.
- Yet another approach is to measure a property (property value) of a target sheet to be separated from the stack of sheets to adjust the charge on the belt accordingly, that is, to control the amount of charges applied to the surface of the seamless dielectric belt, distance between each charge, and period of time to attract the target sheet to the surface of the seamless dielectric belt based on the property value thus measured.
- a property property value
- the above-described control cannot be performed on the target sheet itself separated from the stack of sheets. Further, the above-described control cannot be performed when sheets each having a different property value are included in the same stack of sheets.
- Still yet another approach is to provide a prevention member to the seamless dielectric belt.
- the prevention member is either fixed on or provided movably to the seamless dielectric belt in a direction opposite the direction of sheet feed, with a sheet feed path therebetween.
- a sheet feeding device may include a pickup member contacting a top surface of the stack of sheets to convey the sheets in the direction of sheet feed.
- the pickup member includes a unit to apply alternating charges to the seamless dielectric belt.
- the unit has a charger to form a charge pattern on the surface of the seamless dielectric belt and a neutralizer to remove that charge.
- the pickup member further includes a prevention member to assist to separate the sheets from one another.
- a sheet feeding separation device includes a sheet feeding member and a separation member provided opposite the sheet feeding member. Alternating charges are applied to both the sheet feeding member and the separation member to form an alternating charge pattern on a surface of each of the sheet feeding member and the separation member. Accordingly, the sheet is alternately attracted to and separated from the sheet feeding member and the separation member by an attractive force generated as Maxwell stress.
- the sheet feeding separation device further includes a seamless dielectric belt and a seamless belt serving as a prevention member provided opposite the seamless dielectric belt. Alternatively, a rubber friction pad may be provided as the prevention member.
- JP-A- 2002-211777 discloses an image forming apparatus including a sheet conveyance device including sheet supply means that attracts the sheets using electrostatic attraction to supply the sheets stored in a sheet storage to a conveyance path.
- the sheet conveyance device further includes separation means that uses electrostatic attraction to separate a target sheet to be conveyed from multiple other sheets supplied by the sheet supply means.
- illustrative embodiments described herein provide a sheet feeding device to reliably separate a sheet from a stack of multiple sheets and feed the sheets one by one over time even when a wider variety of sheets is used, and an image forming apparatus including the sheet feeding device.
- At least one embodiment provides a sheet feeding device including a belt including a dielectric material seamlessly wound about rollers and disposed opposite a top surface of a stack of multiple sheets placed on a sheet storage stand to attract a sheet from the stack of multiple sheets and convey the sheet, and a charger to form a predetermined charge pattern on a surface of the belt.
- a shaft of one of the rollers provided downstream from the other roller in a direction of sheet feed serves as a pivot of the belt about which the belt swings, and the belt swings around the pivot such that the surface of the belt facing the top surface of the stack of multiple sheets and a surface of the sheet storage stand facing the surface of the belt are substantially parallel to each other.
- At least one embodiment provides an image forming apparatus including the sheet feeding device described above.
- FIG. 1 is a schematic view illustrating an example of a configuration of an image forming apparatus according to illustrative embodiments
- FIG. 2 is a perspective view illustrating an example of a sheet attraction/separation unit included in a sheet feeding device according to a first illustrative embodiment
- FIG. 3 is a schematic cross-sectional view illustrating the sheet attraction/separation unit illustrated in FIG. 2 ;
- FIGS. 4A and 4B are schematic cross-sectional views illustrating operation of the sheet attraction/separation unit illustrated in FIGS. 2 and 3 ;
- FIG. 5 is a schematic cross-sectional view illustrating a variation of the sheet attraction/separation unit included in the sheet feeding device according to the first illustrative embodiment
- FIGS. 6A to 6D are timing charts each illustrating a control sequence of an applied voltage and a frequency in the sheet feeding device
- FIG. 7 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a second illustrative embodiment
- FIG. 8 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a third illustrative embodiment
- FIG. 9 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a fourth illustrative embodiment
- FIG. 10 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a fifth illustrative embodiment
- FIG. 11 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a sixth illustrative embodiment
- FIG. 12 is a perspective view illustrating a separation unit included in the sheet feeding device according to the sixth illustrative embodiment.
- FIG. 13 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a seventh illustrative embodiment.
- FIG. 1 is a schematic view illustrating an example of a configuration of a copier serving as an image forming apparatus 1 according to illustrative embodiments.
- the image forming apparatus 1 includes a document reading unit 2 , an image forming unit 3 , and a sheet feeder 4 .
- the image forming unit 3 and the sheet feeder 4 are separately formed, and are detachably attachable to each other.
- the sheet feeder 4 includes a sheet feeding device 5 .
- the sheet feeding device 5 includes a sheet attraction/separation unit 7 , a charging roller 8 , and a friction pad 9 .
- the sheet attraction/separation unit 7 contacts a top surface of a stack of sheets 6 stored in a sheet feed cassette, not shown, to attract a top sheet 6 a placed at the top of the stack of sheets 6 , and separates the top sheet 6 a from the stack of sheets 6 .
- the sheet attraction/separation unit 7 is detachably attachable to the sheet feeder 4 .
- the sheet attraction/separation unit 7 attracts the stack of sheets 6 including the top sheet 6 a placed at the top thereof, and the friction pad 9 separates the top sheet 6 a from the stack of sheets 6 .
- the sheets included in the stack of sheets 6 are fed to a pair of registration rollers 11 one by one.
- Each sheet is then conveyed to a transfer device 12 from the pair of registration rollers 11 , and a toner image formed by the image forming unit 3 is transferred onto the sheet in the transfer device 12 .
- the sheet having the toner image thereon is conveyed to a fixing device 13 , and heat and pressure are applied to the sheet to fix the toner image to the sheet.
- the sheet having the fixed toner image thereon is discharged by a discharge roller 14 to a discharge tray 15 .
- the sheet feeding device 5 is also applicable to image forming apparatuses other than the image forming apparatus 1 employing electrophotography, such as inkjet type image forming apparatuses. Further, the sheet feeding device 5 according to illustrative embodiments is applicable to facsimile machines, printers, multifunction devices having two or more of copying, printing, scanning and facsimile functions, and so forth, as well as copiers as described above. It is also to be noted that the sheet feeding device 5 is also known as a sheet feeding/separation device.
- the sheet attraction/separation unit 7 includes a drive roller 22 , a driven roller 23 , and a seamless belt 19 including a dielectric material stretched between the drive roller 22 and the driven roller 23 .
- the belt 19 includes a dielectric material having a resistivity of 10 8 ⁇ cm or greater.
- An example of the dielectric material includes a polyethylene terephthalate film, having a thickness of about 100 ⁇ m.
- the sheet attraction/separation unit 7 further includes a bottom plate 28 and an insulating sheet 29 provided on the bottom plate 28 .
- the insulating sheet 29 enables the bottom plate 28 to be formed of a metal material, providing higher rigidity to the bottom plate 28 . As a result, even a last sheet placed at the bottom of the stack of sheets 6 can be reliably fed to the image forming unit 3 .
- FIG. 3 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 illustrated in FIG. 2 .
- the belt 19 is double-layered, including a top layer 19 a and a bottom layer 19 b.
- the top layer 19 a includes a dielectric material having a resistivity of 10 8 ⁇ cm or greater
- the bottom layer 19 b includes a conductive material having a resistivity of 10 6 ⁇ cm or less.
- a charging electrode 21 can be used as a counter electrode grounded to the bottom layer 19 b, the charging electrode 21 may be provided at any position contacting the surface of the belt 19 , that is, the top layer 19 a.
- the charging electrode 21 including a roller connected to an AC power supply 24 , is provided such that the charging electrode 21 contacts the belt 19 at a position where the belt 19 is wound around the drive roller 22 .
- the stack of sheets 6 is positioned so as to obtain an area of the sheet attracted to the belt 19 sufficient for reliable removal.
- the drive roller 22 includes a conductive rubber layer having a resistivity of about 10 6 ⁇ cm on a surface thereof.
- the driven roller 23 is a metal roller. Both the drive roller 22 and the driven roller 23 are grounded.
- An upper guide plate 26 and a lower guide plate 27 each restricting conveyance of the sheets are provided on a downstream side from the belt 19 relative to a direction of sheet feed.
- the surface of the belt 19 facing the stack of sheets 6 is provided in parallel to a surface of the bottom plate 28 on which the stack of sheets 6 is placed.
- the sheet attraction/separation unit 7 is provided on a downstream side from a leading edge of the top sheet 6 a to be separated from the stack of sheets 6 relative to the direction of sheet feed, such that the leading edge of the top sheet 6 a never contacts the belt 19 including a dielectric material.
- the top sheet 6 a can be effectively removed from the belt 19 using a curvature of the belt 19 .
- the belt 19 swings around a shaft 22 a of the drive roller 22 as a pivot as illustrated in FIG. 4A , and is positioned at a front part of an upper surface of the top sheet 6 A of the stack of sheets 6 to contact the top sheet 6 A.
- the pivot is positioned such that the top surface of the stack of sheets 6 on the bottom plate 28 pushed upward by a spring 37 is on a tangential line to the curvature of the belt 19 on the drive roller 22 side.
- one side of the belt 19 that is, the driven roller 23 side in the case of FIGS. 4A and 4B because the shaft 22 a of the drive roller 22 serves as the pivot as described above, swings to maximize an area of contact between the stack of sheets 6 and the belt 19 .
- the sheet attraction/separation unit 7 is designed to have an attractive force sufficient to remove the top sheet 6 A
- the spring 37 only pushes the stack of sheets 6 upward via the bottom plate 28 such that the stack of sheets 6 touches the sheet attraction/separation unit 7 .
- a force that attracts a next sheet to be fed can be increased, and a space is formed so that the sheets are reliably separated from one another.
- the charging electrode 21 is provided on the drive roller 22 side so that a load applied to the stack of sheet 6 from the sheet attraction/separation unit 7 swung around the shaft 22 a of the drive roller 22 by its own weight is reduced, causing a decrease in a frictional force between the top sheet 6 a and a second sheet 6 b, that is, the second sheet from the top of the stack of sheets 6 .
- the friction pad 9 in the first illustrative embodiment engages the sheet attraction/separation unit 7 , so that the friction pad 9 swings together with the sheet attraction/separation unit 7 .
- an angle of approach of the sheet to the friction pad 9 can be kept constant.
- a retard roller may be used.
- the friction pad 9 and the lower guide member 27 are pushed upward by a spring 38 .
- a pressure applied to the stack of sheets 6 can be kept constant regardless of the number of sheets in the stack of sheets 6 , and a frictional force between each sheet in the stack of sheets 6 can be reduced. Further, the area of contact between the belt 19 and the stack of sheets 6 can be effectively used, providing the ability to consistently separate the stack of sheets 6 from one another without causing multiple sheet feeding and moreover without wrinkling the next sheet.
- FIG. 5 is a schematic cross-sectional view illustrating a variation of the sheet attraction/separation unit 7 .
- the stack of sheets 6 on the bottom plate 28 can be moved upward or downward by a pushing device 40 , and a sensor 30 is provided to detect the upper surface of the top sheet 6 a at the top of the stack of sheets 6 . Accordingly, a distance and a pressure between the belt 19 and the top sheet 6 a can be appropriately controlled.
- the AC power supply 24 may supply a direct current varied between alternating high and low electric potentials as well as an alternating current.
- an alternating current having an amplitude of 4 KV is applied to the surface of the belt 19 .
- FIGS. 6A to 6D are timing charts each showing a control sequence of an applied voltage and a frequency in the sheet feeding device 5 .
- the belt 19 having a charge pattern thereon contacts the front part on the upper surface of the top sheet 6 a at a position where the belt 19 is wound around the driven roller 23 . Accordingly, the Maxwell stress acts on the top sheet 6 a due to a non-uniform electric field formed by the charge pattern on the surface of the belt 19 . As a result, only the top sheet 6 a is attracted to the belt 19 and is conveyed in the direction of sheet feed to the pair of registration rollers 11 through the upper guide member 26 and the lower guide member 27 . Thereafter, the top sheet 6 a is further conveyed to the image forming unit 3 by the pair of registration rollers 11 .
- the force that attracts the top sheet 6 a generated by the charge pattern as described above also acts on the second sheet 6 b and some other sheets beneath the second sheet 6 b for a certain period of time from when the top sheet 6 a is attracted to the belt 19 .
- the force acts only on the top sheet 6 a so that the second sheet 6 b and the other sheets beneath the second sheet 6 b are no longer attracted to the belt 19 . Accordingly, the top sheet 6 a can be separated from the stack of sheets 6 without using a prevention member with enough time.
- the insulating sheet 29 is provided on the contact surface between the bottom plate 28 and the belt 19 to generate a force that attracts the last sheet, that is, the sheet at the bottom of the stack of sheets 6 .
- a neutralizing electrode 25 connected to a neutralizing power supply 16 serving as an alternate power supply is provided on an upstream side from the charging electrode 21 relative to the direction of sheet feed and a downstream side from a position where the sheet is separated from the belt 19 relative to the direction of sheet feed.
- the neutralizing electrode 25 contacts the belt 19 or is provided near the belt 19 .
- the AC power supply 24 and the neutralizing power supply 16 are controlled such that the force on the belt 19 that attracts the sheet is eliminated at a position where the leading edge of the, sheet contacts the pair of registration rollers 11 . Therefore, the sheet sandwiched by the pair of registration rollers 11 is conveyed only by the pair of the registration rollers 11 without being affected by the belt 19 .
- a linear velocity of the pair of registration rollers 11 is the same as that of the belt 19 .
- the belt 19 is driven intermittently.
- the belt 19 is separated from the stack of sheets 6 before a rear edge of the top sheet 6 a reaches a position facing the driven roller 23 so that the second sheet 6 b is not attracted to the belt 19 .
- the sheet is separated from the belt 19 at the drive roller 22 by the curvature of the belt 19 against the drive roller 22 thereat, and further separated from the belt 19 using the upper guide plate 26 and the lower guide plate 27 illustrated in FIG. 3 .
- the top sheet 6 a is attracted to the belt 19 having the alternating charge pattern thereon and is separated from the stack of sheets 6 . Thereafter, the top sheet 6 a passes through the friction pad 9 using friction. Accordingly, even when multiple sheets are attracted to the belt 19 at the same time, those sheets are separated one by one by the friction pad 9 . As a result, the sheets are reliably separated from one another and fed one by one, preventing multiple sheet feeding.
- the sheet feeding device 5 can handle a wider variety of sheets regardless of a coefficient of friction thereof, and provide an image forming apparatus including a sheet feeding device having an ability to reliably separate the sheets one by one.
- FIG. 7 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in the sheet feeding device 5 according to the second illustrative embodiment.
- a separation pick 33 is provided so that the sheet is further reliably separated from the belt 19 using the separation pick 33 as well as the curvature of the belt 19 at the drive roller 22 .
- the rest of the configuration and operations of the sheet feeding device 5 according to the second illustrative embodiment are same as those of the sheet feeding device 5 according to the first illustrative embodiment, and a description thereof is omitted.
- FIG. 8 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in the sheet feeding device 5 according to a third illustrative embodiment.
- the sheet attraction/separation unit 7 is provided on a downstream side from the leading edge of the top sheet 6 a to be separated from the stack of sheets 6 relative to the direction of sheet feed.
- the sheet attraction/separation unit 7 is provided on an upstream side from the leading edge of the top sheet 6 a relative to the direction of sheet feed.
- FIG. 9 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in the sheet feeding device 5 according to a fourth illustrative embodiment.
- a separation unit 31 is provided on a downstream side from the sheet attraction/separation unit 7 relative to the direction of sheet feed.
- the separation unit 31 includes a paper feed roller 18 and a roller member 34 serving as a prevention member provided facing the paper feed roller 18 .
- a one-way clutch, not shown, is provided to the roller member 34 to prevent the roller member 34 from rotating together with conveyance of the sheets.
- the roller member 34 is pressed against the paper feed roller 18 by a spring 34 a.
- the roller member 34 is pressed against the paper feed roller 18 at a very small pressure of, for example, 500 gf or less.
- a very small pressure of, for example, 500 gf or less.
- a coefficient of friction between the roller member 34 and the top sheet 6 a is greater than a coefficient of friction between the top sheet 6 a and the second sheet 6 b. Accordingly, only the top sheet 6 a is supported by the paper feed roller 18 , and is conveyed to a pair of conveyance rollers 17 provided on a downstream side from the paper feed roller 18 relative to the direction of sheet feed.
- FIG. 10 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in the sheet feeding device 5 according to a fifth illustrative embodiment.
- a roller member 35 including a torque limiter is provided facing the paper feed roller 18 in the separation unit 31 .
- the torque limiter causes the roller member 35 to rotate in a direction indicated by an arrow a in FIG. 10 when multiple sheets including the top sheet 6 a and the second sheet 6 b are conveyed between the paper feed roller 18 and the roller member 35 to stop the conveyance of the second sheet 6 b at the roller member 35 and separate the second sheet 6 b from the top sheet 6 a.
- the roller member 35 is rotated in a direction indicated by an arrow b in FIG.
- the sheet attracted to the belt 19 is reliably separated from the belt 19 by the roller member 35 at a predetermined position so that the leading edge of the sheet is reliably guided to the separation unit 31 . Because the leading edge of the top sheet 6 a at the top of the stack of sheets 6 does not contact the belt 19 as described in the first illustrative embodiment, the leading edge of the top sheet 6 a is reliably guided to the separation unit 31 without using secondary means such as a separation pick.
- FIG. 11 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in the sheet feeding device 5 according to a sixth illustrative embodiment.
- FIG. 12 is an enlarged perspective view illustrating the separation unit 31 included in the sheet feeding device 5 according to the sixth illustrative embodiment.
- the separation unit 31 includes the friction pad 9 including a friction member 36 and a bracket 44 .
- the friction member 36 attached to the bracket 44 is provided facing the paper feed roller 18 , and is pressed against the paper feed roller 18 at a very small pressure by a spring 38 .
- an angle of approach of the sheet to the friction pad 9 from the belt 19 can be kept constant, reliably providing the ability to separate the sheets from one another.
- FIG. 13 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in the sheet feeding device 5 according to a seventh illustrative embodiment.
- the sheet is separated from the belt 19 by the curvature of the belt 19 at the drive roller 22 .
- the sheet is separated from the belt 19 using only the upper guide plate 26 . Because the sheet is separated from the surface of the belt 19 without using a separation pick, the number of components can be reduced.
- a friction pad system is employed in the separation unit 31 . Accordingly, a configuration of the separation unit 31 can be simplified, reducing costs and a number of components.
- An image forming apparatus including the sheet feeding device 5 according to the foregoing illustrative embodiments can handle a wider variety of sheets regardless of a coefficient of friction thereof, and reliably separate the sheets from one another.
- illustrative embodiments of the present invention are not limited to those described above, and various modifications and improvements are possible without departing from the scope of the present invention. It is therefore to be understood that, within the scope of the associated claims, illustrative embodiments may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the illustrative embodiments.
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Abstract
A sheet feeding device including a belt including a dielectric material seamlessly wound about rollers and disposed opposite a top surface of a stack of multiple sheets placed on a sheet storage stand to attract a sheet from the stack of multiple sheets and convey the sheet, and a charger to form a predetermined charge pattern on a surface of the belt. A shaft of one of the rollers provided downstream from the other roller in a direction of sheet feed serves as a pivot of the belt about which the belt swings, and the belt swings around the pivot such that the surface of the belt facing the top surface of the stack of multiple sheets and a surface of the sheet storage stand facing the surface of the belt are substantially parallel to each other.
Description
- The present patent application claims priority from Japanese Patent Application No. 2008-201628, filed on Aug. 5, 2008 in the Japan Patent Office, which is hereby incorporated herein by reference in its entirety.
- 1. Technical Field
- Illustrative embodiments described in this patent specification generally relate to a sheet feeding device to separate a stack of sheets and feed the sheets one by one, and an image forming apparatus including the sheet feeding device.
- 2. Description of the Related Art
- Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction devices having two or more of copying, printing, scanning, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of a latent image bearing member (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
- The image forming apparatuses further include a sheet feeding device to feed recording media such as a sheet. A friction paper feed method using a pickup member is widely employed in the sheet feeding device. Examples of the pickup member include a roller and a belt each including a material having a larger coefficient of friction such as rubber. However, although a configuration of the sheet feeding device can be simplified by employing the friction paper feed method, the pickup member needs to be pressed against the sheet using a spring or the like to obtain a larger fictional force. Because the coefficient of friction at the surface of the material having a larger coefficient of friction such as rubber is changed over time and by environmental factors, the friction paper feed method cannot stably provide a higher ability to reliably feed the sheet.
- In recent years, a wider variety of recording media including special paper such as coated paper and label paper have been used as well as plain paper in the image forming apparatuses by diverse users, and it is expected that the number of different types of recording media demanded by users will further increase in the future. However, because the coefficient of friction at the surface of some types of special paper is extremely small, it is often difficult to separate the sheets of special paper from one another using friction alone. Further, peeling may occur at a release part of release paper when the sheets of release paper are frictionally separated from one another using a roller and a pressing member.
- One possible solution to the above-described problems is to employ an air suction method in which negative pressure is generated by air suction to suction and convey the recording media. However, although providing a more reliable ability to feed the recording media compared to the friction paper feed method, the air suction method is noisy and causes an increase in size and costs of the sheet feeding device. Consequently, the air suction method is not practical for image forming apparatuses installed in an office or the like.
- As another approach, a sheet feeding device including a seamless dielectric belt rotated in a direction of sheet feed has been proposed. The seamless dielectric belt contacts a top surface of a stack of sheets, and alternating charges (that is, electrical charges of alternating polarity) are applied to a surface of the seamless dielectric belt by a member. The member includes a charging unit to form an alternating charge pattern on the surface of the seamless dielectric belt and a neutralizing unit to de-charge, or neutralize, the surface of the seamless dielectric belt. The charges thus applied to the surface of the seamless dielectric belt generate an electric field that in turn generates an attractive electrostatic force that attracts the sheet to the surface of the seamless dielectric belt. Accordingly, a sheet placed at the top of the stack of sheets (hereinafter referred to as a top sheet) is separated from the rest of the stack of sheets and is conveyed in the direction of sheet feed.
- However, for a certain period of time after the seamless dielectric belt contacts the top sheet the attractive force thus generated by the electric field tends also to act on multiple other sheets in the stack of sheets as well as the top sheet. Consequently, these multiple other sheets are also attracted to the seamless dielectric belt together with the top sheet, and all sheets are conveyed in the direction of sheet feed without being separated from one another, causing multiple sheet feeding.
- To prevent multiple sheet feeding, a technique in which the sheets are separated from one another and conveyed one by one a predetermined period of time after the seamless dielectric belt contacts the top sheet has been proposed.
- For example, a separation/conveyance device is used that includes an attraction/separation unit to alternately attract and support a top sheet placed at the top of the stack of sheets using an attractive force generated by a non-uniform electric field and separate the top sheet from the stack of sheets. The separation/conveyance device further includes a drive control unit to move the attraction/separation unit, a sheet conveyance unit to convey the top sheet thus separated, and an auxiliary separation unit to assist the attraction/separation unit to separate the top sheet from the stack of sheets. The drive control unit moves the attraction/separation unit from a leading edge side of the top sheet to a predetermined position to contact the top sheet, and stops the attraction/separation unit at that position. After a predetermined period of time elapses, the drive control unit moves the attraction/separation unit again. The auxiliary separation unit applies a predetermined force between the top sheet attracted to the attraction/separation unit and a second sheet, that is, a next sheet placed immediately beneath the top sheet, to separate the top sheet from the second sheet.
- However, although it can prevent multiple sheet feeding, higher-speed sheet feeding cannot be achieved by the above-described separation/conveyance device due to the stop time involved.
- Yet another approach is to measure a property (property value) of a target sheet to be separated from the stack of sheets to adjust the charge on the belt accordingly, that is, to control the amount of charges applied to the surface of the seamless dielectric belt, distance between each charge, and period of time to attract the target sheet to the surface of the seamless dielectric belt based on the property value thus measured.
- However, because the target sheet first needs to be separated from the stack of sheets in order to measure the property value thereof, the above-described control cannot be performed on the target sheet itself separated from the stack of sheets. Further, the above-described control cannot be performed when sheets each having a different property value are included in the same stack of sheets.
- Still yet another approach is to provide a prevention member to the seamless dielectric belt. The prevention member is either fixed on or provided movably to the seamless dielectric belt in a direction opposite the direction of sheet feed, with a sheet feed path therebetween.
- For example, a sheet feeding device may include a pickup member contacting a top surface of the stack of sheets to convey the sheets in the direction of sheet feed. The pickup member includes a unit to apply alternating charges to the seamless dielectric belt. The unit has a charger to form a charge pattern on the surface of the seamless dielectric belt and a neutralizer to remove that charge. The pickup member further includes a prevention member to assist to separate the sheets from one another.
- For another example, a sheet feeding separation device includes a sheet feeding member and a separation member provided opposite the sheet feeding member. Alternating charges are applied to both the sheet feeding member and the separation member to form an alternating charge pattern on a surface of each of the sheet feeding member and the separation member. Accordingly, the sheet is alternately attracted to and separated from the sheet feeding member and the separation member by an attractive force generated as Maxwell stress. The sheet feeding separation device further includes a seamless dielectric belt and a seamless belt serving as a prevention member provided opposite the seamless dielectric belt. Alternatively, a rubber friction pad may be provided as the prevention member.
- However, because the attractive force is also applied to multiple other sheets placed beneath the top sheet as well as the top sheet, it is difficult to reliably separate the sheets from one another using the prevention member.
- Published unexamined Japanese Patent Application No. (hereinafter referred to as JP-A-) 2002-211777 discloses an image forming apparatus including a sheet conveyance device including sheet supply means that attracts the sheets using electrostatic attraction to supply the sheets stored in a sheet storage to a conveyance path. The sheet conveyance device further includes separation means that uses electrostatic attraction to separate a target sheet to be conveyed from multiple other sheets supplied by the sheet supply means.
- In order to reliably attract the sheet to the seamless dielectric belt, it is important to provide a wide contact area between the seamless dielectric belt and the sheet. At the same time, however, although reliable attraction of the sheet to the seamless dielectric belt is required to separate the sheets from one another, a leading edge of the sheet needs to be securely removed from the seamless dielectric belt once the sheets are separated from one another. Further, multiple sheets attracted to the seamless dielectric belt must be reliably separated from one another in order to achieve high-speed sheet feeding without causing multiple sheet feeding.
- In view of the foregoing, illustrative embodiments described herein provide a sheet feeding device to reliably separate a sheet from a stack of multiple sheets and feed the sheets one by one over time even when a wider variety of sheets is used, and an image forming apparatus including the sheet feeding device.
- At least one embodiment provides a sheet feeding device including a belt including a dielectric material seamlessly wound about rollers and disposed opposite a top surface of a stack of multiple sheets placed on a sheet storage stand to attract a sheet from the stack of multiple sheets and convey the sheet, and a charger to form a predetermined charge pattern on a surface of the belt. A shaft of one of the rollers provided downstream from the other roller in a direction of sheet feed serves as a pivot of the belt about which the belt swings, and the belt swings around the pivot such that the surface of the belt facing the top surface of the stack of multiple sheets and a surface of the sheet storage stand facing the surface of the belt are substantially parallel to each other.
- At least one embodiment provides an image forming apparatus including the sheet feeding device described above.
- Additional features and advantages of the illustrative embodiments will be more fully apparent from the following detailed description, the accompanying drawings, and the associated claims.
- A more complete appreciation of the illustrative embodiments described herein and the many attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
-
FIG. 1 is a schematic view illustrating an example of a configuration of an image forming apparatus according to illustrative embodiments; -
FIG. 2 is a perspective view illustrating an example of a sheet attraction/separation unit included in a sheet feeding device according to a first illustrative embodiment; -
FIG. 3 is a schematic cross-sectional view illustrating the sheet attraction/separation unit illustrated inFIG. 2 ; -
FIGS. 4A and 4B are schematic cross-sectional views illustrating operation of the sheet attraction/separation unit illustrated inFIGS. 2 and 3 ; -
FIG. 5 is a schematic cross-sectional view illustrating a variation of the sheet attraction/separation unit included in the sheet feeding device according to the first illustrative embodiment; -
FIGS. 6A to 6D are timing charts each illustrating a control sequence of an applied voltage and a frequency in the sheet feeding device; -
FIG. 7 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a second illustrative embodiment; -
FIG. 8 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a third illustrative embodiment; -
FIG. 9 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a fourth illustrative embodiment; -
FIG. 10 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a fifth illustrative embodiment; -
FIG. 11 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a sixth illustrative embodiment; -
FIG. 12 is a perspective view illustrating a separation unit included in the sheet feeding device according to the sixth illustrative embodiment; and -
FIG. 13 is a schematic cross-sectional view illustrating a sheet attraction/separation unit included in a sheet feeding device according to a seventh illustrative embodiment. - The accompanying drawings are intended to depict illustrative embodiments and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.
- In describing illustrative embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve a similar result.
- Reference is now made to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.
-
FIG. 1 is a schematic view illustrating an example of a configuration of a copier serving as an image forming apparatus 1 according to illustrative embodiments. The image forming apparatus 1 includes adocument reading unit 2, animage forming unit 3, and asheet feeder 4. In the image forming apparatus 1, theimage forming unit 3 and thesheet feeder 4 are separately formed, and are detachably attachable to each other. - The
sheet feeder 4 includes asheet feeding device 5. Thesheet feeding device 5 includes a sheet attraction/separation unit 7, a chargingroller 8, and afriction pad 9. The sheet attraction/separation unit 7 contacts a top surface of a stack ofsheets 6 stored in a sheet feed cassette, not shown, to attract atop sheet 6 a placed at the top of the stack ofsheets 6, and separates thetop sheet 6 a from the stack ofsheets 6. According to illustrative embodiments, the sheet attraction/separation unit 7 is detachably attachable to thesheet feeder 4. - Specifically, the sheet attraction/
separation unit 7 attracts the stack ofsheets 6 including thetop sheet 6 a placed at the top thereof, and thefriction pad 9 separates thetop sheet 6 a from the stack ofsheets 6. Accordingly, the sheets included in the stack ofsheets 6 are fed to a pair ofregistration rollers 11 one by one. Each sheet is then conveyed to atransfer device 12 from the pair ofregistration rollers 11, and a toner image formed by theimage forming unit 3 is transferred onto the sheet in thetransfer device 12. Thereafter, the sheet having the toner image thereon is conveyed to a fixingdevice 13, and heat and pressure are applied to the sheet to fix the toner image to the sheet. The sheet having the fixed toner image thereon is discharged by adischarge roller 14 to adischarge tray 15. - It is to be noted that the
sheet feeding device 5 according to illustrative embodiments is also applicable to image forming apparatuses other than the image forming apparatus 1 employing electrophotography, such as inkjet type image forming apparatuses. Further, thesheet feeding device 5 according to illustrative embodiments is applicable to facsimile machines, printers, multifunction devices having two or more of copying, printing, scanning and facsimile functions, and so forth, as well as copiers as described above. It is also to be noted that thesheet feeding device 5 is also known as a sheet feeding/separation device. - A description is now given of the sheet attraction/
separation unit 7 included in thesheet feeding device 5 according to a first illustrative embodiment with reference toFIG. 2 . - The sheet attraction/
separation unit 7 includes adrive roller 22, a drivenroller 23, and aseamless belt 19 including a dielectric material stretched between thedrive roller 22 and the drivenroller 23. Specifically, thebelt 19 includes a dielectric material having a resistivity of 108 Ωcm or greater. An example of the dielectric material includes a polyethylene terephthalate film, having a thickness of about 100 μm. The sheet attraction/separation unit 7 further includes abottom plate 28 and an insulatingsheet 29 provided on thebottom plate 28. The insulatingsheet 29 enables thebottom plate 28 to be formed of a metal material, providing higher rigidity to thebottom plate 28. As a result, even a last sheet placed at the bottom of the stack ofsheets 6 can be reliably fed to theimage forming unit 3. -
FIG. 3 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 illustrated inFIG. 2 . As illustrated inFIG. 3 , thebelt 19 is double-layered, including atop layer 19 a and abottom layer 19 b. Thetop layer 19 a includes a dielectric material having a resistivity of 108 Ωcm or greater, and thebottom layer 19 b includes a conductive material having a resistivity of 106 Ωcm or less. Because a chargingelectrode 21 can be used as a counter electrode grounded to thebottom layer 19 b, the chargingelectrode 21 may be provided at any position contacting the surface of thebelt 19, that is, thetop layer 19 a. According to the first illustrative embodiment, the chargingelectrode 21, including a roller connected to anAC power supply 24, is provided such that the chargingelectrode 21 contacts thebelt 19 at a position where thebelt 19 is wound around thedrive roller 22. The stack ofsheets 6 is positioned so as to obtain an area of the sheet attracted to thebelt 19 sufficient for reliable removal. Thedrive roller 22 includes a conductive rubber layer having a resistivity of about 106 Ωcm on a surface thereof. The drivenroller 23 is a metal roller. Both thedrive roller 22 and the drivenroller 23 are grounded. Anupper guide plate 26 and alower guide plate 27 each restricting conveyance of the sheets are provided on a downstream side from thebelt 19 relative to a direction of sheet feed. Specifically, the surface of thebelt 19 facing the stack ofsheets 6 is provided in parallel to a surface of thebottom plate 28 on which the stack ofsheets 6 is placed. Further, the sheet attraction/separation unit 7 is provided on a downstream side from a leading edge of thetop sheet 6 a to be separated from the stack ofsheets 6 relative to the direction of sheet feed, such that the leading edge of thetop sheet 6 a never contacts thebelt 19 including a dielectric material. As a result, thetop sheet 6 a can be effectively removed from thebelt 19 using a curvature of thebelt 19. - The
belt 19 swings around ashaft 22 a of thedrive roller 22 as a pivot as illustrated inFIG. 4A , and is positioned at a front part of an upper surface of the top sheet 6A of the stack ofsheets 6 to contact the top sheet 6A. The pivot is positioned such that the top surface of the stack ofsheets 6 on thebottom plate 28 pushed upward by aspring 37 is on a tangential line to the curvature of thebelt 19 on thedrive roller 22 side. - In addition, one side of the
belt 19, that is, the drivenroller 23 side in the case ofFIGS. 4A and 4B because theshaft 22 a of thedrive roller 22 serves as the pivot as described above, swings to maximize an area of contact between the stack ofsheets 6 and thebelt 19. Because the sheet attraction/separation unit 7 is designed to have an attractive force sufficient to remove the top sheet 6A, thespring 37 only pushes the stack ofsheets 6 upward via thebottom plate 28 such that the stack ofsheets 6 touches the sheet attraction/separation unit 7. Further, a force that attracts a next sheet to be fed can be increased, and a space is formed so that the sheets are reliably separated from one another. - The charging
electrode 21 is provided on thedrive roller 22 side so that a load applied to the stack ofsheet 6 from the sheet attraction/separation unit 7 swung around theshaft 22 a of thedrive roller 22 by its own weight is reduced, causing a decrease in a frictional force between thetop sheet 6 a and asecond sheet 6 b, that is, the second sheet from the top of the stack ofsheets 6. - Further, returning to
FIG. 3 , thefriction pad 9 in the first illustrative embodiment engages the sheet attraction/separation unit 7, so that thefriction pad 9 swings together with the sheet attraction/separation unit 7. As a result, an angle of approach of the sheet to thefriction pad 9 can be kept constant. In place of thefriction pad 9, for example, a retard roller may be used. As illustrated inFIG. 3 , thefriction pad 9 and thelower guide member 27 are pushed upward by aspring 38. - When driving of the
drive roller 22 is stopped, a free edge side of thebottom plate 28 is pushed upward by thespring 37 as illustrated inFIG. 4B , and one edge side of the sheet attraction/separation unit 7 is moved upward due to swinging movement. It is to be noted that a stopper, not shown, that keeps the sheet attraction/separation unit 7 swingingly moved upward horizontal may be preferably provided. Specifically, when a free edge of thebottom plate 28 pushed upward contacts the pivot of thebelt 19, only the weight of thebelt 19 keeps thebelt 19 in contact with the stack ofsheets 6. Accordingly, a pressure applied to the stack ofsheets 6 can be kept constant regardless of the number of sheets in the stack ofsheets 6, and a frictional force between each sheet in the stack ofsheets 6 can be reduced. Further, the area of contact between thebelt 19 and the stack ofsheets 6 can be effectively used, providing the ability to consistently separate the stack ofsheets 6 from one another without causing multiple sheet feeding and moreover without wrinkling the next sheet. -
FIG. 5 is a schematic cross-sectional view illustrating a variation of the sheet attraction/separation unit 7. As illustrated inFIG. 5 , the stack ofsheets 6 on thebottom plate 28 can be moved upward or downward by a pushingdevice 40, and asensor 30 is provided to detect the upper surface of thetop sheet 6 a at the top of the stack ofsheets 6. Accordingly, a distance and a pressure between thebelt 19 and thetop sheet 6 a can be appropriately controlled. - It is to be noted that the
AC power supply 24 may supply a direct current varied between alternating high and low electric potentials as well as an alternating current. In the first illustrative embodiment, an alternating current having an amplitude of 4 KV is applied to the surface of thebelt 19.FIGS. 6A to 6D are timing charts each showing a control sequence of an applied voltage and a frequency in thesheet feeding device 5. - The
belt 19 having a charge pattern thereon contacts the front part on the upper surface of thetop sheet 6 a at a position where thebelt 19 is wound around the drivenroller 23. Accordingly, the Maxwell stress acts on thetop sheet 6 a due to a non-uniform electric field formed by the charge pattern on the surface of thebelt 19. As a result, only thetop sheet 6 a is attracted to thebelt 19 and is conveyed in the direction of sheet feed to the pair ofregistration rollers 11 through theupper guide member 26 and thelower guide member 27. Thereafter, thetop sheet 6 a is further conveyed to theimage forming unit 3 by the pair ofregistration rollers 11. The force that attracts thetop sheet 6 a generated by the charge pattern as described above also acts on thesecond sheet 6 b and some other sheets beneath thesecond sheet 6 b for a certain period of time from when thetop sheet 6 a is attracted to thebelt 19. However, after the certain period of time has elapsed, the force acts only on thetop sheet 6 a so that thesecond sheet 6 b and the other sheets beneath thesecond sheet 6 b are no longer attracted to thebelt 19. Accordingly, thetop sheet 6 a can be separated from the stack ofsheets 6 without using a prevention member with enough time. - As illustrated in
FIG. 2 , the insulatingsheet 29 is provided on the contact surface between thebottom plate 28 and thebelt 19 to generate a force that attracts the last sheet, that is, the sheet at the bottom of the stack ofsheets 6. Further, as illustrated inFIG. 3 , a neutralizingelectrode 25 connected to a neutralizingpower supply 16 serving as an alternate power supply is provided on an upstream side from the chargingelectrode 21 relative to the direction of sheet feed and a downstream side from a position where the sheet is separated from thebelt 19 relative to the direction of sheet feed. The neutralizingelectrode 25 contacts thebelt 19 or is provided near thebelt 19. In the sheet attraction/separation unit 7 according to the first illustrative embodiment, theAC power supply 24 and the neutralizingpower supply 16 are controlled such that the force on thebelt 19 that attracts the sheet is eliminated at a position where the leading edge of the, sheet contacts the pair ofregistration rollers 11. Therefore, the sheet sandwiched by the pair ofregistration rollers 11 is conveyed only by the pair of theregistration rollers 11 without being affected by thebelt 19. - A description is now given of operations of the
sheet feeding device 5. When an electromagnetic clutch is turned on in response to a sheet feed signal, thedrive roller 22 is driven to rotate thebelt 19. Alternating charges are applied to thebelt 19 from theAC power supply 24 through the chargingelectrode 21 so that a charge pattern alternating with a pitch corresponding to an AC power frequency and a rotation speed of thebelt 19 is formed on the surface of thebelt 19. It is to be noted that the pitch is preferably set in a range from 5 mm to 15 mm. - A linear velocity of the pair of
registration rollers 11 is the same as that of thebelt 19. When the pair ofregistration rollers 11 is driven intermittently with intervals, thebelt 19 is driven intermittently. Thebelt 19 is separated from the stack ofsheets 6 before a rear edge of thetop sheet 6 a reaches a position facing the drivenroller 23 so that thesecond sheet 6 b is not attracted to thebelt 19. The sheet is separated from thebelt 19 at thedrive roller 22 by the curvature of thebelt 19 against thedrive roller 22 thereat, and further separated from thebelt 19 using theupper guide plate 26 and thelower guide plate 27 illustrated inFIG. 3 . - According to the first illustrative embodiment, the
top sheet 6 a is attracted to thebelt 19 having the alternating charge pattern thereon and is separated from the stack ofsheets 6. Thereafter, thetop sheet 6 a passes through thefriction pad 9 using friction. Accordingly, even when multiple sheets are attracted to thebelt 19 at the same time, those sheets are separated one by one by thefriction pad 9. As a result, the sheets are reliably separated from one another and fed one by one, preventing multiple sheet feeding. - It is preferable to provide a cleaning mechanism for the
belt 19 in order to prevent paper dust and other foreign substances attached to thebelt 19 from disturbing attraction of the sheets to thebelt 19. - The
sheet feeding device 5 according to the first illustrative embodiment can handle a wider variety of sheets regardless of a coefficient of friction thereof, and provide an image forming apparatus including a sheet feeding device having an ability to reliably separate the sheets one by one. - A description is now given of the
sheet feeding device 5 according to a second illustrative embodiment.FIG. 7 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in thesheet feeding device 5 according to the second illustrative embodiment. As illustrated inFIG. 7 , aseparation pick 33 is provided so that the sheet is further reliably separated from thebelt 19 using theseparation pick 33 as well as the curvature of thebelt 19 at thedrive roller 22. The rest of the configuration and operations of thesheet feeding device 5 according to the second illustrative embodiment are same as those of thesheet feeding device 5 according to the first illustrative embodiment, and a description thereof is omitted. -
FIG. 8 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in thesheet feeding device 5 according to a third illustrative embodiment. In the foregoing illustrative embodiments, the sheet attraction/separation unit 7 is provided on a downstream side from the leading edge of thetop sheet 6 a to be separated from the stack ofsheets 6 relative to the direction of sheet feed. By contrast, according to the third illustrative embodiment, the sheet attraction/separation unit 7 is provided on an upstream side from the leading edge of thetop sheet 6 a relative to the direction of sheet feed. As a result, a number of drive transmission parts can be reduced compared to the case in which thedrive roller 22 is provided on the free edge side of thebottom plate 28, and the weight of thebelt 19 can be reduced. -
FIG. 9 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in thesheet feeding device 5 according to a fourth illustrative embodiment. As illustrated inFIG. 9 , in thesheet feeding device 5 according to the fourth illustrative embodiment, aseparation unit 31 is provided on a downstream side from the sheet attraction/separation unit 7 relative to the direction of sheet feed. Theseparation unit 31 includes apaper feed roller 18 and aroller member 34 serving as a prevention member provided facing thepaper feed roller 18. A one-way clutch, not shown, is provided to theroller member 34 to prevent theroller member 34 from rotating together with conveyance of the sheets. Theroller member 34 is pressed against thepaper feed roller 18 by aspring 34a. Specifically, theroller member 34 is pressed against thepaper feed roller 18 at a very small pressure of, for example, 500 gf or less. When multiple sheets including thetop sheet 6 a and thesecond sheet 6 b are attracted and conveyed by thebelt 19, thesecond sheet 6 b is separated from thetop sheet 6 a by friction between thesecond sheet 6 b and theroller member 34, and conveyance of thesecond sheet 6 b is stopped at theroller member 34. Because the pressure applied to thepaper feed roller 18 from theroller member 34 is very small, conveyance of thetop sheet 6 a frictionally supported by thepaper feed roller 18 is not prevented. More specifically, a coefficient of friction between theroller member 34 and thetop sheet 6 a is greater than a coefficient of friction between thetop sheet 6 a and thesecond sheet 6 b. Accordingly, only thetop sheet 6 a is supported by thepaper feed roller 18, and is conveyed to a pair ofconveyance rollers 17 provided on a downstream side from thepaper feed roller 18 relative to the direction of sheet feed. -
FIG. 10 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in thesheet feeding device 5 according to a fifth illustrative embodiment. As illustrated inFIG. 10 , aroller member 35 including a torque limiter is provided facing thepaper feed roller 18 in theseparation unit 31. The torque limiter causes theroller member 35 to rotate in a direction indicated by an arrow a inFIG. 10 when multiple sheets including thetop sheet 6 a and thesecond sheet 6 b are conveyed between thepaper feed roller 18 and theroller member 35 to stop the conveyance of thesecond sheet 6 b at theroller member 35 and separate thesecond sheet 6 b from thetop sheet 6 a. By contrast, theroller member 35 is rotated in a direction indicated by an arrow b inFIG. 10 along with rotation of the paper feed-roller 18 by a friction when only thetop sheet 6 a is conveyed between thepaper feed roller 18 and theroller member 35. Theroller member 35 is pressed against thepaper feed roller 18 by aspring 35 a. The rest of the configuration and operations of thesheet feeding device 5 according to the fifth illustrative embodiment are same as those of thesheet feeding device 5 according to the fourth illustrative embodiment, and a description thereof is omitted. - In the
sheet feeding device 5 according to the fifth illustrative embodiment, the sheet attracted to thebelt 19 is reliably separated from thebelt 19 by theroller member 35 at a predetermined position so that the leading edge of the sheet is reliably guided to theseparation unit 31. Because the leading edge of thetop sheet 6 a at the top of the stack ofsheets 6 does not contact thebelt 19 as described in the first illustrative embodiment, the leading edge of thetop sheet 6 a is reliably guided to theseparation unit 31 without using secondary means such as a separation pick. -
FIG. 11 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in thesheet feeding device 5 according to a sixth illustrative embodiment.FIG. 12 is an enlarged perspective view illustrating theseparation unit 31 included in thesheet feeding device 5 according to the sixth illustrative embodiment. As illustrated inFIGS. 11 and 12 , theseparation unit 31 includes thefriction pad 9 including afriction member 36 and abracket 44. Thefriction member 36 attached to thebracket 44 is provided facing thepaper feed roller 18, and is pressed against thepaper feed roller 18 at a very small pressure by aspring 38. The rest of the configuration and operations of thesheet feeding device 5 according to the sixth illustrative embodiment are same as those of thesheet feeding device 5 according to the fifth illustrative embodiment, and a description thereof is omitted. According to the sixth illustrative embodiment, an angle of approach of the sheet to thefriction pad 9 from thebelt 19 can be kept constant, reliably providing the ability to separate the sheets from one another. -
FIG. 13 is a schematic cross-sectional view illustrating the sheet attraction/separation unit 7 included in thesheet feeding device 5 according to a seventh illustrative embodiment. As described above, in the foregoing illustrative embodiments, the sheet is separated from thebelt 19 by the curvature of thebelt 19 at thedrive roller 22. By contrast, in the seventh illustrative embodiment, the sheet is separated from thebelt 19 using only theupper guide plate 26. Because the sheet is separated from the surface of thebelt 19 without using a separation pick, the number of components can be reduced. - Further, in the seventh illustrative embodiment, a friction pad system is employed in the
separation unit 31. Accordingly, a configuration of theseparation unit 31 can be simplified, reducing costs and a number of components. - An image forming apparatus including the
sheet feeding device 5 according to the foregoing illustrative embodiments can handle a wider variety of sheets regardless of a coefficient of friction thereof, and reliably separate the sheets from one another. - It is to be noted that illustrative embodiments of the present invention are not limited to those described above, and various modifications and improvements are possible without departing from the scope of the present invention. It is therefore to be understood that, within the scope of the associated claims, illustrative embodiments may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the illustrative embodiments.
Claims (15)
1. A sheet feeding device, comprising:
a belt comprising a dielectric material seamlessly wound about rollers and disposed opposite a top surface of a stack of multiple sheets placed on a sheet storage stand to attract a sheet from the stack of multiple sheets and convey the sheet; and
a charger to form a predetermined charge pattern on a surface of the belt,
wherein:
a shaft of one of the rollers provided downstream from the other roller in a direction of sheet feed serves as a pivot of the belt about which the belt swings; and
the belt swings around the pivot such that the surface of the belt facing the top surface of the stack of multiple sheets and a surface of the sheet storage stand facing the surface of the belt are substantially parallel to each other.
2. The sheet feeding device according to claim 1 , wherein a leading edge of the stack of multiple sheets is positioned opposite a bottom part of a curved portion of the belt on a downstream side relative to the direction of sheet feed.
3. The sheet feeding device according to claim 1 , wherein the charger is provided adjacent to the pivot of the belt.
4. The sheet feeding device according to claim 1 , wherein a pivot-side roller around which the belt is wound is rotatably driven.
5. The sheet feeding device according to claim 1 , further comprising an upper guide plate provided downstream from a leading edge side of the stack of multiple sheets placed on a sheet storage stand in the direction of sheet feed,
wherein a surface of a curved portion of the belt provided downstream in the direction of sheet feed intersects with the upper guide plate.
6. The sheet feeding device according to claim 1 , further comprising a biasing member to lift a free edge of the belt opposite an end of the belt at the pivot.
7. The sheet feeding device according to claim 1 , further comprising a unit to keep the belt horizontal at an uppermost position at a top of an arc through which the belt swings.
8. The sheet feeding device according to claim 1 , further comprising an insulating sheet disposed on a bottom plate portion of the sheet feeding device,
wherein at least a portion of the insulating sheet disposed near the surface of the sheet storage stand contacting the belt comprises an insulating material.
9. The sheet feeding device according to claim 1 , further comprising a unit to feed each sheet from the stack of multiple sheets using frictional force between the unit and sheets at a position where the sheets are separated from the belt.
10. The sheet feeding device according to claim 1 , further comprising a separation unit contacting the belt, wherein the separation unit swings together with the belt.
11. The sheet feeding device according to claim 10 , wherein the separation unit comprises a separation pick.
12. The sheet feeding device according to claim 10 , wherein the separation unit comprises a friction pad.
13. The sheet feeding device according to claim 10 , wherein the separation unit comprises a separation roller.
14. The sheet feeding device according to claim 13 , wherein the separation roller is reversely rotatable.
15. An image forming apparatus comprising a sheet feeding device, the sheet feeding device comprising:
a belt comprising a dielectric material seamlessly wound about rollers and disposed opposite a top surface of a stack of multiple sheets placed on a sheet storage stand to attract a sheet from the stack of multiple sheets and convey the sheet; and
a charger to form a predetermined-charge pattern on a surface of the belt,
wherein:
a shaft of one of the rollers provided downstream from the other roller in a direction of sheet feed serves as a pivot of the belt about which the belt swings; and
the belt swings around the pivot such that the surface of the belt facing the top surface of the stack of multiple sheets and a surface of the sheet storage stand facing the surface of the belt are substantially parallel to each other.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2008201628A JP2010037047A (en) | 2008-08-05 | 2008-08-05 | Sheet material feeder and image forming device using the same |
JP2008-201628 | 2008-08-05 |
Publications (1)
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US20100032891A1 true US20100032891A1 (en) | 2010-02-11 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/461,185 Abandoned US20100032891A1 (en) | 2008-08-05 | 2009-08-04 | Sheet feeding device and image forming apparatus |
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JP (1) | JP2010037047A (en) |
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JP5685943B2 (en) | 2011-01-05 | 2015-03-18 | 株式会社リコー | Sheet material feeding apparatus and image forming apparatus |
JP5776966B2 (en) | 2011-03-10 | 2015-09-09 | 株式会社リコー | Sheet conveying apparatus and image forming apparatus |
JP2014177325A (en) * | 2013-03-14 | 2014-09-25 | Ricoh Co Ltd | Paper feeder and image formation apparatus |
JP6218011B2 (en) * | 2013-05-16 | 2017-10-25 | 株式会社リコー | Sheet conveying apparatus and image forming apparatus |
JP6218017B2 (en) * | 2013-07-01 | 2017-10-25 | 株式会社リコー | Sheet conveying apparatus and image forming apparatus |
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Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
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US20100296851A1 (en) * | 2009-05-20 | 2010-11-25 | Ricoh Company, Ltd. | Sheet feeding device and electrophotographic image forming apparatus |
US8157257B2 (en) * | 2009-05-20 | 2012-04-17 | Ricoh Company, Ltd. | Sheet feeding device and electrophotographic image forming apparatus with rotating charged belt |
US20110052227A1 (en) * | 2009-09-03 | 2011-03-03 | Ricoh Company, Ltd. | Image forming apparatus |
US8752821B2 (en) * | 2009-09-03 | 2014-06-17 | Ricoh Company, Limited | Image forming apparatus |
US8439479B2 (en) * | 2009-11-11 | 2013-05-14 | Seiko Epson Corporation | Liquid ejecting apparatus |
US20110109709A1 (en) * | 2009-11-11 | 2011-05-12 | Seiko Epson Corporation | Liquid ejecting apparatus |
US20110115865A1 (en) * | 2009-11-19 | 2011-05-19 | Seiko Epson Corporation | Liquid ejecting apparatus |
US8382240B2 (en) * | 2009-11-19 | 2013-02-26 | Seiko Epson Corporation | Liquid ejecting apparatus |
CN102674040A (en) * | 2011-03-10 | 2012-09-19 | 株式会社理光 | Sheet feeder and image forming apparatus |
US9898122B2 (en) | 2011-05-12 | 2018-02-20 | Google Technology Holdings LLC | Touch-screen device and method for detecting and ignoring false touch inputs near an edge of the touch-screen device |
US20130234385A1 (en) * | 2012-03-09 | 2013-09-12 | Katsuhito Suzuki | Print medium feeding apparatus with electrode in endless belt |
US10488303B2 (en) * | 2012-11-08 | 2019-11-26 | Sakura Finetek Japan Co., Ltd. | Replacement blade supplying mechanism |
US20170174455A1 (en) * | 2014-08-22 | 2017-06-22 | Canon Kabushiki Kaisha | Sheet feeding apparatus and image forming apparatus |
US10179715B2 (en) | 2017-03-27 | 2019-01-15 | Brother Kogyo Kabushiki Kaisha | Sheet-feeding device including second feeding roller for feeding sheets in addition to first feeding roller |
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Owner name: RICOH COMPANY, LTD.,JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TOGASHI, TOSHIFUMI;HIGAKI, HIDETO;REEL/FRAME:023080/0570 Effective date: 20090723 |
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