Paper feeder

Abstract

To provide a paper feeder capable of suppressing feeding failure of a sheet.SOLUTION: A paper feeder according to an embodiment comprises a paper-feeding tray, a pickup roller, an upper face guide, and a pair of lifting members. The paper-feeding tray is provided with a placement face on which a sheet bundle obtained by laminating sheets is placed. The pickup roller conveys a sheet of an uppermost layer of the sheet bundle onto a downstream side in a conveyance direction. The upper face guide is possible to come into contact with the sheet conveyed from above the paper-feeding tray to a downstream side, from above. The pair of lifting members are arranged so as to be spaced apart at an interval in a horizontal width direction orthogonal to the conveyance direction. The pair of lifting members lift both ends in a width direction of the sheet bundle by extending upward from the placement face. An upper end face of the pair of lifting members comes into contact with the sheet bundle. An end on a downstream side on the upper end face is located on an upper stream side in the conveyance direction than an end on a downstream side of the sheet bundle.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Embodiments of the present invention relate to a sheet feeding device.

Background Art

[0002] An image forming apparatus forms an image on a sheet. The image forming apparatus has a sheet feeding device that feeds the sheet. There is a need for a sheet feeding device that can suppress poor feeding of the sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a sheet feeding device that can suppress poor feeding of the sheet.

Means for Solving the Problems

[0005] The sheet feeding device according to the embodiment includes a sheet feeding tray, a pickup roller, an upper guide, and a pair of lifting members. The sheet feeding tray has a placement surface on which a sheet stack on which sheets are stacked is placed. The pickup roller conveys the uppermost sheet in the sheet stack to the downstream side in the conveyance direction. The upper guide can contact the sheet conveyed downstream from above the sheet feeding tray. The pair of lifting members are arranged at intervals in the horizontal width direction orthogonal to the conveyance direction. The pair of lifting members project upward from the placement surface and lift both end portions in the width direction of the sheet stack. The upper end surfaces of the pair of lifting members contact the sheet stack. The downstream end portion of the upper end surface is located upstream of the downstream end portion of the sheet stack in the conveyance direction.

Brief Description of the Drawings

[0006]

Figure 1

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Figure 16

Mode for Carrying Out the Invention

[0007] Hereinafter, the paper feeding device of the embodiment will be described with reference to the drawings.

[0008] First, the configuration of the image forming apparatus 10 of the embodiment will be described with reference to FIG. 1. FIG. 1 is an explanatory drawing showing an example of the configuration of the image forming apparatus 10. For example, the image forming apparatus 10 is arranged in a workplace such as an office.

[0009] In the present application, the Z-direction, X-direction, and Y-direction in the orthogonal coordinate system are defined as follows. The Z-direction is the vertical direction of the image forming apparatus 10, and the +Z direction is the upward direction. The X-direction is the left-right direction of the image forming apparatus 10, and the +X direction is the right direction. The Y-direction (width direction) is the front-back direction of the image forming apparatus 10. In the Y-direction, the side closer to the center of the paper feed cassette 51 may be referred to as the inner side, and the side farther from the center may be referred to as the outer side. For example, the Z-direction is the vertical direction, and the X-direction and Y-direction are the horizontal directions.

[0010] In FIG. 1, the image forming apparatus 10 includes a control panel 13, a wireless tag communication device 90, and a printer unit 18. The printer unit 18 includes a control unit 100, a paper feed cassette 51, a conveyance device 60, and the like. The control unit 100 controls the control panel 13, the wireless tag communication device 90, and the printer unit 18. The control unit 100 controls the conveyance of the sheet in the printer unit 18. The control of the sheet conveyance is to control the conveyance timing of the sheet, the stop position of the sheet, the conveyance speed of the sheet, and the like.

[0011] The control panel 13 includes an input key and a display unit. For example, the input key receives an input from the user. For example, the display unit is a touch panel type. The display unit receives an input from the user and displays information to the user. For example, the control panel 13 displays items related to the operation of the image forming apparatus 10 on the display unit so that they can be set. The control panel 13 notifies the control unit 100 of the items set by the user.

[0012] The paper feed cassette 51 stores sheets provided with wireless tags. Note that the paper feed cassette 51 can also store sheets not provided with wireless tags. In the following description, unless otherwise specified, the sheet is a sheet provided with a wireless tag. For the sheet, materials such as paper and plastic film are used, for example.

[0013] The printer unit 18 performs an operation of forming an image. For example, the printer unit 18 forms an image indicated by image data on a sheet. In the following description, forming an image on a sheet is also referred to as "printing". Note that in the present embodiment, the printer unit 18 is a device that fixes a toner image, but it is not limited thereto, and it may be an inkjet type device.

[0014] The printer unit 18 includes an intermediate transfer belt 21. The printer unit 18 supports the intermediate transfer belt 21 with a driven roller 41, a backup roller 40, and the like. The printer unit 18 rotates the intermediate transfer belt 21 in the direction of arrow m. The printer unit 18 includes four sets of image forming stations 22Y, 22M, 22C, and 22K. Each of the image forming stations 22Y, 22M, 22C, and 22K corresponds to Y (yellow), M (magenta), C (cyan), and K (black), respectively. The image forming stations 22Y, 22M, 22C, and 22K are arranged below the intermediate transfer belt 21 along the rotation direction of the intermediate transfer belt 21.

[0015] Hereinafter, among the image forming stations 22Y, 22M, 22C, and 22K, the image forming station 22Y for Y (yellow) will be described as an example. Note that since the image forming stations 22M, 22C, and 22K have the same configuration as the image forming station 22Y, detailed description thereof will be omitted.

[0016] The image forming station 22Y includes a primary transfer roller 30. The primary transfer roller 30 is disposed to face the photosensitive drum 24 via the intermediate transfer belt 21.

[0017] The image forming station 22Y includes a charging charger 26, an exposure scanning head 27, a developing device 28, and a photosensitive cleaner 29. The charging charger 26, the exposure scanning head 27, the developing device 28, and the photosensitive cleaner 29 are disposed around the photosensitive drum 24 that rotates in the direction of arrow n.

[0018] The charging charger 26 uniformly charges the photoreceptor drum 24. The exposure scanning head 27 exposes the uniformly charged photoreceptor drum 24 to form an electrostatic latent image on the photoreceptor drum 24. The developing device 28 develops the electrostatic latent image on the photoreceptor drum 24 using a two-component developer formed of toner and carrier.

[0019] The primary transfer roller 30 primarily transfers the toner image formed on the photoreceptor drum 24 to the intermediate transfer belt 21. By each primary transfer roller 30 of the image forming stations 22Y, 22M, 22C, and 22K primarily transferring the toner image onto the intermediate transfer belt 21, a color toner image is formed on the intermediate transfer belt 21. The color toner image is a toner image formed by sequentially overlapping toner images of Y (yellow), M (magenta), C (cyan), and K (black). The photoreceptor cleaner 29 removes the toner remaining on the photoreceptor drum 24 after primary transfer.

[0020] The printer unit 18 includes a secondary transfer roller 32. The secondary transfer roller 32 is disposed to face the backup roller 40 via the intermediate transfer belt 21. The secondary transfer roller 32 secondarily transfers the color toner image on the intermediate transfer belt 21 to the sheet all at once. In the following description, when the term "toner image" is used, it may be either a color toner image or a toner image of only one color. Also, the toner image may be a toner image using decolorizing toner.

[0021] The conveyance path 33 is a path along which a sheet is conveyed by a plurality of conveyance rollers (for example, conveyance roller 330, etc.). The conveyance path 33 includes a first conveyance path 33a, a second conveyance path 33b, and a third conveyance path 33c. The first conveyance path 33a is a conveyance path from the merging portion 44a to the branching portion 44b. The second conveyance path 33b is a conveyance path that passes through the duplex printing device 38 and is a conveyance path different from the first conveyance path 33a from the branching portion 44b to the merging portion 44a. The third conveyance path 33c is a conveyance path from the branching portion 44b to the paper discharge tray 20.

[0022] The sheet is taken out from the sheet placement section 16 of either the paper feed cassette 51 or the manual feed tray 16c. The sheet taken out from the sheet placement section 16 is temporarily stopped at the portion where it is in contact with the two stationary registration rollers 31. At this time, the leading edge of the sheet abuts against the registration rollers 31, and the inclination of the sheet is corrected. The control unit 100 starts the rotation of the registration rollers 31 in accordance with the position of the toner image on the rotating intermediate transfer belt 21 and moves the sheet to the position of the secondary transfer roller 32.

[0023] The toner image formed on the intermediate transfer belt 21 is secondarily transferred onto the sheet by the secondary transfer roller 32. Further, the secondarily transferred toner image is fixed onto the sheet by the fixing device 34. In this way, an image is formed on the sheet under the control of the control unit 100. The control unit 100 conveys the sheet on which the toner image has been fixed by the fixing device 34 to the third conveyance path 33c and discharges the sheet.

[0024] The wireless tag communication device 90 includes an arithmetic device, a storage device, and an antenna (not shown). The wireless tag in the present embodiment is, for example, an RFID (Radio Frequency Identifier) tag. The wireless tag communication device 90 transmits radio waves in the direction of arrow k, for example. The wireless tag communication device 90 communicates with the wireless tag provided on the sheet via the antenna. Specifically, the wireless tag communication device 90 reads information from the wireless tag and writes information to the wireless tag.

[0025] The information written to the wireless tag includes, for example, information indicating the contents, information indicating the destination, and the contents printed on the sheet when the sheet is used for logistics or the like. In the present embodiment, the wireless tag communication device 90 uses, for example, a radio wave system (UHF) in the 900 MHz band. However, the RFID system and frequency band are not limited to this, and other systems and frequency bands can also be adopted.

[0026] The control unit 100 controls each part of the image forming apparatus 10. Figure 2 is a hardware configuration diagram of the image processing apparatus. As shown in Figure 2, the image forming apparatus 10 includes a CPU (Central Processing Unit) 91, a memory 92, an auxiliary storage device 93, etc. connected by a bus, and executes programs. The image forming apparatus 10 functions as a device including a printer unit 18, a control panel 13, and a wireless tag communication device 90 by executing programs.

[0027] The CPU 91 functions as a control unit 100 by executing programs stored in the memory 92 and the auxiliary storage device 93. The control unit 100 controls the operations of each functional unit of the image forming apparatus 10. The auxiliary storage device 93 is configured using a storage device such as a magnetic hard disk device or a semiconductor storage device. The auxiliary storage device 93 stores information.

[0028] Figure 3 is a plan view of the sheet S having the wireless tag T. In Figure 3, the sheet S in a state of being accommodated in the paper feed cassette 51 is shown. In Figure 3, the thickness direction of the sheet S coincides with the Z direction, and the width direction coincides with the Y direction.

[0029] For example, the sheet S is a regular sheet. The image forming apparatus 10 forms an image on regular sheets of various sizes. Among the sizes of regular sheets, the sizes of the A series such as A4 are defined in the international standard ISO216 that defines the paper dimensions. The sizes of the B series such as B5 are defined in ISO216 or the Japanese Industrial Standard JIS-B series. LT is the letter size and is defined as ANSI A in the American National Standards Institute ANSI / ASME Y14.1. LG is the legal size. In the present application, among the regular sheets on which image formation is possible in the image forming apparatus 10, the regular sheet having the maximum width in the Y direction is defined as the maximum regular sheet.

[0030] The sheet S has a wireless tag T. The wireless tag T is disposed inside the sheet S in the thickness direction. The wireless tag T may be attached to the surface of the sheet S. For example, the wireless tag T is disposed at the +X-direction end in the central portion of the sheet S in the Y direction. The wireless tag T may be disposed at a position different from that in FIG. 3. The wireless tag T is rectangular when viewed from the Z direction. For example, the wireless tag T is disposed on the sheet S with its longitudinal direction aligned with the X direction and its short-side direction aligned with the Y direction. The wireless tag T may be disposed on the sheet S in a posture different from that in FIG. 3.

[0031] The wireless tag T includes an antenna A and an IC chip C. The antenna A transmits and receives radio waves and the like to and from the wireless tag communication device 90. The IC chip C records and processes information. The wireless tag T has a thickness in the Z direction. The thickness of the sheet S at the portion where the wireless tag T is disposed is thicker than other portions. In particular, the thickness of the sheet S at the portion where the IC chip C is disposed is thicker than other portions.

[0032] FIG. 4 is a perspective view of the paper feed cassette 51. FIG. 5 is a cross-sectional view of the paper feed cassette 51 and the conveying device 60 at a position corresponding to the V-V line in FIG. 4. As shown in FIGS. 4 and 5, the paper feed cassette 51 is box-shaped and opens in the +Z direction. The paper feed cassette 51 accommodates a sheet bundle SS (see FIGS. 9 and 10) in which a plurality of sheets S having wireless tags T are stacked in the thickness direction. The paper feed cassette 51 includes a cassette front wall 52, a cassette bottom wall 53, side guides 54, a sheet accommodation space 55, and a paper feed tray 56.

[0033] The cassette front wall 52 is a side wall of the paper feed cassette 51 in the +X direction. The cassette front wall 52 extends from the +Z-direction opening end of the paper feed cassette 51 in the -Z direction. The cassette front wall 52 faces the +X-direction end of the sheet S accommodated in the paper feed cassette 51. The cassette bottom wall 53 extends from the -Z-direction end of the cassette front wall 52 in the -X direction. The cassette bottom wall 53 extends parallel to the XY plane.

[0034] The side guides 54 are arranged inside the paper feed cassette 51. The side guides 54 are plate-shaped and parallel to the XZ plane. A pair of side guides 54 are arranged apart in the Y direction. The pair of side guides 54 can move synchronously inward and outward in the Y direction. The pair of side guides 54 abut against both ends of the sheet S in the Y direction to align the sheet S in the Y direction. The center of the sheet S in the Y direction is arranged at the center of the paper feed cassette 51 in the Y direction.

[0035] The sheet storage space 55 is the space in the -X direction of the cassette front wall 52 and inside the pair of side guides 54 in the Y direction. The sheet storage space 55 can accommodate the maximum regular sheet. The sheet storage space 55 can accommodate the sheet bundle SS.

[0036] The paper feed tray 56 is arranged at the bottom of the sheet storage space 55. The paper feed tray 56 has a placement surface 57 on which the sheet bundle SS is placed. The paper feed tray 56 is movable up and down. The reference state of the paper feed tray 56 is the state where it has descended to the lowered end position up to the cassette bottom wall 53. In the reference state of the paper feed tray 56, the placement surface 57 faces the +Z direction. The paper feed tray 56 is rotatable about the rotation axis P. The paper feed tray 56 moves up and down by rotating about the rotation axis P. The rotation axis P is parallel to the Y direction. The rotation axis P is located in the -X direction relative to the +X direction end of the paper feed tray 56. By the rotation of the paper feed tray 56, the +X direction end of the paper feed tray 56 moves in the Z direction. When the paper feed tray 56 rotates from the reference state, the +X direction end of the sheet bundle SS moves in the +Z direction. Note that FIGS. 4 to 8 show the state where the paper feed tray 56 has rotated from the reference state. Between the pair of side guides 54, the -X direction end of the placement surface 57 is located at the intermediate portion in the X direction in the sheet storage space 55. The cassette bottom wall 53 can support the -X direction end of the sheet bundle SS placed on the placement surface 57.

[0037] FIG. 6 is a perspective view of the conveying device 60. As shown in FIGS. 5 and 6, the conveying device 60 includes a pickup roller 71, a conveying guide 61, and a paper feed roller 72 and a separating roller 73.

[0038] The pickup roller 71 is arranged in the +Z direction of the paper feed cassette 51. The pickup roller 71 is arranged at a position corresponding to the +X-direction end at the central part in the Y direction of the paper feed cassette 51. The pickup roller 71 abuts on the central part in the Y direction of the sheet bundle SS. The pickup roller 71 rotates about a rotation axis Q parallel to the Y direction. The pickup roller 71 is rotationally driven by a motor or the like. The pickup roller 71 is movable in the Z direction independently of the paper feed tray 56.

[0039] The paper feed operation of the pickup roller 71 will be described. In the standby state of the image forming apparatus 10, the paper feed tray 56 descends to the cassette bottom wall 53, and the pickup roller 71 ascends in the +Z direction. The user of the image forming apparatus 10 pulls out the paper feed cassette 51 from the image forming apparatus 10. The user fills the sheet bundle SS into the sheet storage space 55 of the paper feed cassette 51.

[0040] The user pushes the paper feed cassette 51 into the image forming apparatus 10. The pickup roller 71 descends. The paper feed tray 56 rotates to raise the +X-direction end of the sheet bundle SS. The pickup roller 71 abuts on the upper surface of the topmost sheet S in the raised sheet bundle SS. When the pickup roller 71 ascends to a predetermined position, the rotation switch of the pickup roller 71 is turned on. The rotation of the paper feed tray 56 stops. This state is shown. The pickup roller 71 rotates to supply the topmost sheet S from the paper feed cassette 51 in the +W direction.

[0041] Each time the sheet S is supplied, the pickup roller 71 descends little by little. When the pickup roller 71 descends to a predetermined position, the rotation switch of the pickup roller 71 is turned off. The rotation of the pickup roller 71 stops. The paper feed tray 56 rotates to raise the +X-direction end of the sheet bundle SS and the pickup roller 71. When the pickup roller 71 ascends to a predetermined position, the rotation switch of the pickup roller 71 is turned on. The pickup roller 71 rotates to resume the supply of the sheet S.

[0042] In this application, the W direction (conveying direction) is the direction in which the sheet S is conveyed from the paper feed cassette 51. The W direction is along the placement surface 57 as viewed from the Y direction. The +W direction is the downstream side in the direction in which the sheet S is conveyed. The -W direction is the upstream side in the direction in which the sheet S is conveyed and is the opposite side of the +W direction. The conveying device 60 supplies the sheet S from the paper feed cassette 51 in the +W direction. The cassette front wall 52 is the side wall of the paper feed cassette 51 in the +W direction of the sheet storage space 55. In the present embodiment, the W direction is orthogonal to the Y direction, and the +W direction is a direction between the +Z direction and the +X direction.

[0043] The conveyance guide 61 is disposed in the +Z direction of the paper feed cassette 51. The conveyance guide 61 guides the conveyance of the sheet S supplied from the paper feed cassette 51 in the +W direction. The conveyance guide 61 has an upper surface guide 62. The upper surface guide 62 is plate-shaped along the WY plane. However, the upper surface guide 62 does not have to be parallel to the WY plane. The upper surface guide 62 is not displaceable in the Z direction. Note that at least a part of the upper surface guide 62 may be displaceable in the Z direction independently of the paper feed tray 56. For example, a part of the upper surface guide 62 may be displaceable in the Z direction in synchronization with the pickup roller 71. The upper surface guide 62 is at least at the +Z direction position of the cassette front wall 52. The upper surface guide 62 extends along both sides in the W direction from the +Z direction portion of the cassette front wall 52. The -W direction end portion of the upper surface guide 62 is at a position in the -W direction from the rotation axis Q of the pickup roller 71. The -W direction end portion of the upper surface guide 62 is at a position in the +W direction from the upper edge of the lifting member 80. The upper surface guide 62 can contact the upper surface of the sheet S conveyed in the +W direction from the paper feed cassette 51.

[0044] FIG. 7 is a cross-sectional view of the paper feed cassette 51 and the conveyance device 60 at a position corresponding to the line VII-VII in FIG. 6. FIG. 8 is a cross-sectional view of the paper feed cassette 51 and the conveyance device 60 at a position corresponding to the line VIII-VIII in FIG. 6. As shown in FIGS. 7 and 8, a pair of upper surface guides 62 are arranged apart from each other in the Y direction. The pair of upper surface guides 62 are on opposite sides of each other with the pickup roller 71 interposed therebetween. The upper surface guide 62 is arranged in the +Z direction relative to the portion of the pickup roller 71 that contacts the sheet S.

[0045] As shown in FIGS. 5 and 6, the paper feed roller 72 and the separation roller 73 are arranged in the +W direction of the pickup roller 71. The paper feed roller 72 and the separation roller 73 are arranged side by side in the normal direction of the WY plane. The paper feed roller 72 and the separation roller 73 are in contact with each other to form a nip N. The sheet S guided by the conveyance guide 61 and conveyed in the +W direction reaches the nip N.

[0046] The paper feed roller 72 and the separation roller 73 rotate about a rotation axis parallel to the Y direction. The paper feed roller 72 is rotationally driven by a motor or the like. The separation roller 73 has a torque limiter. A plurality of sheets S may be supplied from the paper feed cassette 51 in an overlapping manner. The plurality of sheets S reach the nip N. The lower sheet S stops at the position of the separation roller 73 due to the action of the torque limiter of the separation roller 73. The upper sheet S is conveyed in the +W direction by the paper feed roller 72. After the upper sheet S is conveyed, the stopped lower sheet S is conveyed in the +W direction by the paper feed roller 72. The paper feed roller 72 and the separation roller 73 separate a plurality of sheets S supplied in an overlapping manner from the paper feed cassette 51 and convey them in the +W direction.

[0047] As shown in FIGS. 4 and 5, the paper feed cassette 51 further includes a lifting member 80. The lifting member 80 is disposed in the sheet storage space 55. The whole of the lifting member 80 is located in the -X direction relative to the cassette front wall 52. The lifting member 80 protrudes in the +Z direction from the placement surface 57 of the paper feed tray 56. The lifting member 80 is supported by the paper feed tray 56. The lifting member 80 is displaced integrally with the paper feed tray 56 by the rotation of the paper feed tray 56. The pair of lifting members 80 are arranged apart in the Y direction. The pair of lifting members 80 are arranged at equal intervals in the Y direction with respect to the center in the Y direction in the sheet storage space 55. The lifting member 80 is non-displaceable in the Y direction. By being non-displaceable in the Y direction, each lifting member 80 can take a state of being arranged along the side guide 54 on the same side in the Y direction and a state of being arranged with a gap in the Y direction with respect to the side guide 54 on the same side in the Y direction. The lifting member 80 is arranged at both ends in the Y direction of the sheet storage space 55 in a state of being arranged along the side guide 54 on the same side in the Y direction.

[0048] The lifting member 80 has a length in the W direction. The longitudinal direction of the lifting member 80 is the X direction in the reference state of the paper feed tray 56. The lifting member 80 has a substantially constant width in the Y direction. The -W direction end of the lifting member 80 is located in the -W direction relative to the -W direction end of the placement surface 57 of the paper feed tray 56 between the pair of side guides 54. The -W direction end of the lifting member 80 is notched so as to avoid contacting the cassette bottom wall 53 at a position in the -X direction relative to the placement surface 57 when the lifting member 80 is displaced integrally with the paper feed tray 56.

[0049] The lifting member 80 includes an upper end surface 81 and an inclined surface 82. The upper end surface 81 extends along the longitudinal direction of the lifting member 80. The upper end surface 81 extends parallel to the placement surface 57 of the paper feed tray 56. The upper end surface 81 extends in the W direction with a constant width when viewed from the Z direction. The upper end surface 81 is located in the -Z direction relative to the +Z direction edge of the side guide 54. The upper end surface 81 is a convex curved surface in the +Z direction. The -W direction end of the upper end surface 81 is located in the -W direction relative to the -W direction end of the placement surface 57 of the paper feed tray 56 between the pair of side guides 54. The inclined surface 82 is disposed closer to the +W direction end of the lifting member 80 than the upper end surface 81. The inclined surface 82 extends from the +W direction end of the upper end surface 81 toward the +W direction end side of the lifting member 80. The inclined surface 82 extends in the W direction with the same width as the upper end surface 81 when viewed from the Z direction. The inclined surface 82 extends toward the placement surface 57 side of the paper feed tray 56 as it goes in the +W direction from the +W direction end of the upper end surface 81. The inclined surface 82 extends at a constant inclination angle with respect to the upper end surface 81. The inclined surface 82 has substantially the same cross-sectional shape as the upper end surface 81.

[0050] As shown in FIG. 7, the entire inclined surface 82 and the +W direction end portion 811 of the upper end surface 81 are located in the -W direction relative to the +W direction end of the paper feed tray 56. The entire inclined surface 82 and the +W direction end portion 811 of the upper end surface 81 are located in the -W direction relative to the +W direction end of the sheet bundle SS placed on the placement surface 57 of the paper feed tray 56 (see FIG. 9). The entire inclined surface 82 and the +W direction end portion 811 of the upper end surface 81 are located in the -W direction relative to the rotation axis Q of the pickup roller 71. The entire inclined surface 82 and the +W direction end portion 811 of the upper end surface 81 are located in the -W direction relative to the -W direction end of the upper surface guide 62.

[0051] The state of the sheet S accommodated in the sheet accommodation space 55 will be described. As shown in FIG. 3, the sheet S has a wireless tag T at the +X direction end in the central portion of the sheet S in the Y direction. The thickness of the central portion of the sheet S in the Y direction is thicker than other portions due to the arrangement of the wireless tag T.

[0052] FIG. 9 is a front view of the paper feed cassette 51. FIG. 10 is a right side view of the paper feed cassette 51 shown in FIG. 9. As shown in FIGS. 9 and 10, the sheet stack SS is placed on the placement surface 57 of the paper feed tray 56. The thickness of the sheet stack SS at the central portion in the Y direction is thicker than that of other portions. The thickness of the sheet stack SS decreases from the central portion in the Y direction toward the ends. The paper feed tray 56 rises from the lowered end position until the central portion in the Y direction of the sheet stack SS contacts the pickup roller 71 and the pickup roller 71 is pushed up by the sheet stack SS to reach a predetermined position.

[0053] The sheet stack SS contacts the upper end surfaces 81 of a pair of lifting members 80 arranged apart in the Y direction. The portions inside the both ends in the Y direction of the sheet stack SS contact the upper end surfaces 81 of the lifting members 80. The both ends in the Y direction of the sheet stack SS are lifted from the placement surface 57 of the paper feed tray 56 by the lifting members 80. Hereinafter, the reference for the height of the sheet stack SS and the lifting members 80 is the placement surface 57. The height at which the both ends in the Y direction of the sheet stack SS are lifted by the lifting members 80 does not have to coincide with the height of the upper end surfaces 81 of the lifting members 80. For example, the both ends in the Y direction of the sheet stack SS are lifted higher than the height of the upper end surfaces 81 of the lifting members 80 by the stiffness of the sheet S. The end in the +W direction of the sheet stack SS is located in the +W direction from the end in the +W direction of the upper end surface 81 of the lifting member 80. The sheet stack SS may be non-contact with the inclined surface 82 (see FIG. 5) of the lifting member 80. Both corners located at the end in the Y direction at the end in the +W direction of the sheet stack SS are lifted by the stiffness of the sheet stack SS and are non-contact with the placement surface 57. Hereinafter, the ends in the +W direction of the sheet stack SS and the sheet S are referred to as the downstream ends.

[0054] The number of sheet stacks SS shown in FIGS. 9 and 10 is the stackable number. At the downstream end of the sheet stack SS with the stackable number, the heights of both corner portions in the Y direction are lower than those of other portions. At the downstream end of the sheet stack SS with the stackable number, the height of the central portion in the Y direction is higher than those of other portions. At both end portions in the Y direction of the topmost sheet S in the sheet stack SS with the stackable number, they hang down with respect to the central portion in the Y direction. Here, the distance in the Z direction between the cassette front wall 52 and the contact point with the sheet S on the pickup roller 71 is defined as distance A. At the downstream end of the sheet stack SS with the stackable number, the difference between the height of the central portion in the Y direction and the heights of both corner portions in the Y direction coincides with distance A. The topmost sheet S in the sheet stack SS with the stackable number is conveyed in the +W direction by the pickup roller 71 without being caught by the cassette front wall 52. As the discharge of the sheet S progresses and the number of sheets in the sheet stack SS decreases, the paper feed tray 56 and the lifting member 80 rise integrally.

[0055] As the number of sheets in the sheet stack SS increases from the stackable number, both end portions in the Y direction of the topmost sheet S in the sheet stack SS hang down more greatly with respect to the central portion in the Y direction. Since distance A is invariant, the topmost sheet S in the sheet stack SS with a number of sheets more than the stackable number is caught by the cassette front wall 52 when being conveyed in the +W direction by the pickup roller 71.

[0056] FIG. 11 is a front view of the paper feed cassette 51, showing a state in which the discharge of the sheet S has progressed from the state shown in FIG. 9. FIG. 12 is a right side view of the paper feed cassette 51 shown in FIG. 11. In the state shown in FIGS. 11 and 12, the number of sheets in the sheet stack SS is a first number less than the stackable number. At the downstream end of the sheet stack SS with the first number, the heights of both corner portions in the Y direction coincide with the height of the central portion in the Y direction. The topmost sheet S in the sheet stack SS with the first number is conveyed in the +W direction by the pickup roller 71 without being caught by the cassette front wall 52.

[0057] FIG. 13 is a front view of the sheet feeding cassette 51, showing a state in which the discharge of the sheet S has progressed from the state shown in FIG. 11. FIG. 14 is a right side view of the sheet feeding cassette 51 shown in FIG. 13. In the state shown in FIGS. 13 and 14, the number of sheets in the sheet bundle SS is a second number that is less than the first number. At the downstream end of the sheet bundle SS of the second number, the heights of both corner portions in the Y direction are higher than those of other portions. At the downstream end of the sheet bundle SS of the second number, the height of the central portion in the Y direction is lower than those of other portions. Here, the distance in the Z direction between the upper surface guide 62 and the contact point with the sheet S on the pickup roller 71 is defined as the distance B. At the downstream end of the sheet bundle SS of the second number, the difference between the height of the central portion in the Y direction and the heights of both corner portions in the Y direction coincides with the distance B. The second number is the minimum number of sheets in the sheet bundle SS that does not contact the upper surface guide 62. The uppermost sheet S in the sheet bundle SS of the second number is conveyed in the +W direction by the pickup roller 71 without being caught by the upper surface guide 62.

[0058] FIG. 15 is a front view of the sheet feeding cassette 51, showing a state in which the discharge of the sheet S has progressed from the state shown in FIG. 13. FIG. 16 is a right side view of the sheet feeding cassette 51 shown in FIG. 15. In the states shown in FIGS. 15 and 16, the number of sheets in the sheet bundle SS is a third number that is less than the second number. The third number includes one sheet. At the downstream end of the sheet bundle SS of the third number, the heights of both corner portions in the Y direction are higher than other portions. At the downstream end of the sheet bundle SS of the third number, the height of the central portion in the Y direction is lower than other portions. Both corner portions in the Y direction at the downstream end of the sheet bundle SS of the third number contact the upper surface guide 62 from the -Z direction. The upper end surface 81 of the lifting member 80 does not exist in the -Z direction of both corner portions in the Y direction at the downstream end of the sheet bundle SS of the third number. Both corner portions in the Y direction at the downstream end of the sheet bundle SS of the third number are displaced toward the mounting surface 57 side as the sheet feeding tray 56 rises without being inhibited by the upper end surface 81 of the lifting member 80 by contacting the upper surface guide 62. At the downstream end of the sheet bundle SS of the third number, the difference between the height of the central portion in the Y direction and the height of both corner portions in the Y direction coincides with the distance B. The contact force of the upper surface guide 62 applied to the uppermost sheet S of the sheet bundle SS is set to such an extent that it does not inhibit the conveyance of the sheet S. The uppermost sheet S in the sheet bundle SS of the third number is conveyed in the +W direction by the pickup roller 71 without being caught by the upper surface guide 62.

[0059] In this embodiment, a pair of lifting members 80 are provided which project in the +Z direction from the placement surface 57 of the paper feed tray 56 and lift both end portions of the sheet stack SS in the Y direction. If the lifting members 80 were not provided, even when the number of sheets in the sheet stack SS is relatively small, both end portions of the uppermost sheet S of the sheet stack SS in the Y direction might droop with respect to the central portion. This aspect of the sheet stack SS becomes more prominent as the number of sheets in the sheet stack SS increases. When both end portions of the uppermost sheet S in the Y direction droop, the corners on the outer side in the Y direction at the end portion of the sheet S in the +W direction might get caught during conveyance. Specifically, the central portion of the uppermost sheet S in the Y direction contacts the pickup roller 71, and the corner on the outer side in the Y direction at the downstream end of the uppermost sheet S might interfere with the cassette front wall 52 positioned in the -Z direction with respect to the pickup roller 71. According to this embodiment, since both end portions of the sheet stack SS in the Y direction are lifted by the lifting members 80, it is difficult for both end portions of the uppermost sheet S of the sheet stack SS in the Y direction to droop with respect to the central portion. Therefore, not only when the number of sheets in the sheet stack SS is relatively small, but also when the number of sheets in the sheet stack SS is relatively large, it becomes difficult for the sheet S to get caught during conveyance, and it is possible to increase the maximum number of sheets that can be loaded on the paper feed tray 56.

[0060] Furthermore, when the number of sheets in the sheet stack SS is relatively small, by both end portions of the sheet stack SS in the Y direction being lifted by the lifting members 80, both end portions of the uppermost sheet S in the Y direction might be positioned in the +Z direction with respect to the central portion. When both end portions of the uppermost sheet S in the Y direction are positioned in the +Z direction with respect to the central portion, the corners in the Y direction at the downstream end of the uppermost sheet S might get caught by the upper surface guide 62 during conveyance. In this embodiment, the lifting member 80 includes an upper end surface 81 that contacts the sheet stack SS. The +W-direction end of the upper end surface 81 of the lifting member 80 is located in the -W direction relative to the downstream end of the sheet stack SS. According to this configuration, the lifting member 80 does not come into contact with the downstream end of the sheet stack SS. The downstream end of the sheet stack SS is not sandwiched between the lifting member 80 and the upper surface guide 62. The Y-direction corner at the downstream end of the sheet stack SS can be pushed down even if it contacts the upper surface guide 62. Therefore, the contact pressure of the sheet stack SS against the upper surface guide 62 is reduced, and the uppermost sheet S can be conveyed in the +W direction without being caught. As described above, the sheet feeding device 1 can suppress poor feeding of the sheet S.

[0061] The lifting member 80 is not in contact with the downstream end of the sheet stack SS in a state where the second-number sheet stack SS contacts the pickup roller 71. According to this configuration, when the number of sheets in the sheet stack SS is less than the second number, a space for downward displacement is provided at the downstream end of the sheet stack SS. Therefore, a configuration that exhibits the above-described operational effects can be obtained.

[0062] In the sheet stack SS having a number of sheets less than the second number, the Y-direction corner at its downstream end is configured to be able to contact the upper surface guide 62 from below, and is displaced toward the placement surface 57 side of the sheet feeding tray 56 when contacting the upper surface guide 62. According to this configuration, when the Y-direction corner at the downstream end of the sheet stack SS contacts the upper surface guide 62, the contact pressure of the sheet stack SS against the upper surface guide 62 is reduced. Therefore, a configuration that exhibits the above-described operational effects can be obtained.

[0063] The +W-direction end of the upper end surface 81 of the lifting member 80 is located in the -W direction relative to the -W-direction end of the upper surface guide 62. According to this configuration, the sheet stack SS is not sandwiched between the upper end surface 81 of the lifting member 80 and the upper surface guide 62. Therefore, when the Y-direction corner at the downstream end of the sheet stack SS contacts the upper surface guide 62, it is pushed down with a smaller contact pressure. Therefore, the uppermost sheet S can be conveyed in the +W direction without being caught.

[0064] The lifting member 80 has an inclined surface 82 that extends toward the placement surface 57 side from the end portion in the +W direction of the upper end surface 81 as it goes in the +W direction. According to this configuration, the corner portion corresponding to the end portion in the +W direction of the upper end surface 81 of the lifting member 80 becomes an obtuse angle when viewed from the Y direction. Therefore, it is possible to prevent the lifting member 80 from biting into the sheet bundle SS pushed down by the upper surface guide 62. Further, when the downstream end of the sheet bundle SS is pushed down by the upper surface guide 62, the sheet bundle SS can also be supported by the inclined surface 82. Thereby, it is possible to prevent the downstream end of the sheet bundle SS from being excessively pushed down by the upper surface guide 62.

[0065] The end portion in the +W direction of the upper end surface 81 of the lifting member 80 is located in the -W direction with respect to the pickup roller 71. According to this configuration, the contact portion of the sheet bundle SS with the upper end surface 81 of the lifting member 80 and the contact portion with the pickup roller 71 are displaced in the W direction. For this reason, it is possible to prevent the lifting member 80 or the pickup roller 71 from biting into the sheet bundle SS due to the lifting member 80 and the pickup roller 71 approaching each other.

[0066] The upper end surface 81 of the lifting member 80 is a convex curved surface facing upward. According to this configuration, it is possible to prevent the upper end surface 81 of the lifting member 80 from biting into the sheet bundle SS.

[0067] The lifting members 80 are arranged at equal intervals in the Y direction with respect to the center in the Y direction between the pair of side guides 54. According to this configuration, both end portions of the sheet bundle SS in the Y direction are lifted symmetrically in the Y direction. Therefore, it is possible to prevent the posture of the conveyed sheet S from being disrupted, and it becomes difficult for the sheet S to get caught during conveyance. Therefore, poor supply of the sheet S is suppressed.

[0068] The central portion of the sheet stack SS in the Y direction is thicker than both end portions of the sheet stack SS in the Y direction. According to this configuration, when the lifting member 80 is not provided, both end portions in the Y direction of the topmost sheet S hang down with respect to the central portion regardless of the number of sheets in the sheet stack SS. Therefore, by providing the lifting member 80, the above-described effects can be effectively achieved.

[0069] The sheet S has a wireless tag T at the central portion in the Y direction. According to this configuration, the central portion of the sheet stack SS in the Y direction becomes thicker than both end portions. Therefore, it becomes an optimal configuration for achieving the above-described effects.

[0070] In the above-described embodiment, the sheet stack SS is configured to be moved in the Z direction by rotating and inclining the paper feed tray 56. However, the paper feed tray may be configured to move the sheet stack in the Z direction by linearly moving in the Z direction.

[0071] In the above-described embodiment, the lifting member 80 includes an inclined surface 82. However, the lifting member may not include an inclined surface.

[0072] In the above-described embodiment, the lifting member 80 is not displaceable in the Y direction. However, the lifting member may be displaceable in the Y direction. For example, the lifting member may be displaced in the Y direction integrally with the side guide 54 on the same side in the Y direction. In this case, the lifting member only needs to be able to lift both end portions in the width direction of the sheet stack, and may be arranged along the side guide on the same side in the width direction, or may be arranged with a gap in the width direction with respect to the side guide.

[0073] According to at least one of the embodiments described above, since the end portion on the downstream side in the conveyance direction on the upper end surface of the lifting member is located upstream of the end portion on the downstream side in the conveyance direction of the sheet stack, the topmost sheet can be conveyed without being caught on the downstream side in the conveyance direction. Therefore, the paper feeding device can suppress poor supply of sheets.

[0074] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

[0075] The invention described in the specification and drawings of the present application is appended below. (Appendix 1) A paper feed tray having a placement surface on which a stack of sheets with sheets laminated thereon is placed, A pickup roller that conveys the uppermost sheet in the sheet stack to the downstream side in the conveyance direction, An upper surface guide that can contact the sheet conveyed to the downstream side from above the paper feed tray from above, A pair of lifting members that are arranged at intervals in the horizontal width direction orthogonal to the conveyance direction, project upward from the placement surface, lift both end portions in the width direction of the sheet stack, and the downstream end portion of the upper end surface that contacts the sheet stack is located upstream of the downstream end portion of the sheet stack in the conveyance direction, A paper feed device comprising: (Appendix 2) The downstream end portion of the upper end surface of the lifting member is located upstream of the pickup roller, The paper feed device according to Appendix 1. (Appendix 3) The upper end surface of the lifting member is a convex curved surface upward, The paper feed device according to Appendix 1 or Appendix 2. (Appendix 4) The paper feed device further comprises a pair of side guides for aligning the sheet stack in the width direction, The lifting members are arranged at equal intervals in the width direction with respect to the center in the width direction between the pair of side guides, The paper feed device according to any one of Appendix 1 to Appendix 3. (Appendix 5) The central part of the sheet bundle in the width direction is thicker than both end parts of the sheet bundle in the width direction. The paper feeding device according to any one of Appendices 1 to 4. (Appendix 6) The sheet has a wireless tag at the central part in the width direction. The paper feeding device according to Appendix 5.

Explanation of Reference Numerals

[0076] 56…Paper feeding tray, 57…Placement surface, 62…Upper surface guide, 71…Pickup roller, 80…Lifting member, 81…Upper end surface, 82…Inclined surface, S…Sheet, SS…Sheet bundle

Claims

1. a sheet feed tray having a placement surface on which a sheet stack having stacked sheets is placed; a pickup roller configured to convey the uppermost sheet in the sheet stack downstream in a conveying direction; an upper surface guide capable of contacting from above the sheet conveyed from the sheet feed tray to the downstream side; a pair of lifting members arranged at an interval in a horizontal width direction perpendicular to the conveying direction, protruding upward from the placement surface to lift both ends of the sheet stack in the width direction, and the downstream end of an upper end surface that contacts the sheet stack is located upstream of the downstream end of the sheet stack in the conveying direction; A paper feeding device comprising:

2. the paper feed tray is movable up and down relative to the pickup roller and the upper surface guide; a non-contact number is defined as a minimum number of sheets of the sheet stack that do not contact the upper surface guide when the sheet feed tray is raised from the lower end position and the sheet stack contacts the pickup roller; the pair of lifting members are not in contact with the downstream end of the sheet stack when the non-contact number of sheets of the sheet stack are in contact with the pickup roller; The paper feeder according to claim 1 .

3. the sheet stack has a corner portion on the downstream side and on an outer side in the width direction, the corner portion of the sheet stack, the number of sheets of which is less than the non-contact number, is displaced toward the placement surface by contacting the upper surface guide while the sheet stack is in contact with the pickup roller; The paper feeder according to claim 2 .

4. The downstream end of the upper end surface of the lifting member is located upstream of the upstream end of the upper surface guide. The paper feeder according to any one of claims 1 to 3.

5. The lifting member has an inclined surface extending from the downstream end of the upper end surface toward the placement surface toward the downstream side. The paper feeder according to any one of claims 1 to 3.

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