Sheet feeding device and image forming device

Abstract

To provide a sheet feeding device which can smoothly feed even a sheet whose thickness is not uniform, with a simple structure.SOLUTION: A sheet feeding device 70 includes: a sheet loading part 72; a reference fence 73; an end fence 74; push-out means (blower device 82) for pushing out the sheet on the uppermost layer of a sheet bundle into a conveyance direction; and conveyance means (conveyance belt 91, pickup roller 55c) for coming into contact with the uppermost layer of the sheet bundle loaded on the sheet loading part, and conveying the sheets one by one from the reference fence to the downstream side. Second loading parts (73a, 73b, 73c) are formed extending from an upper end part of the reference fence to the downstream side at predetermined length and opposing to the conveyance means, and the uppermost layer sheet pushed out to the second loading part by the push-out means is conveyed to the downstream side one by one by the conveyance means.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to a sheet feeding device for feeding sheets such as paper, and an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine or a printing machine equipped with the sheet feeding device.

Background Art

[0002] As a sheet feeding device for a printer or an electrophotographic copying machine, etc., a sheet feeding device is generally used in which the upper surface of a stack of sheets loaded in a paper loading section is brought into contact with a sheet feeding belt or a sheet feeding roller, and sheets are sequentially fed from the uppermost layer of the stack of sheets (see Patent Documents 1 and 2). The sheet feeding belt and the sheet feeding roller are intermittently rotationally driven in response to a sheet feeding signal.

[0003] In recent years, particularly for laser printers, there has been an increasing diversification of the papers to be printed, and there has been an increasing demand for directly printing on papers with non-uniform thickness such as envelopes. However, an envelope has a flap side with an opening that is the thinnest, while the glued side at the bottom is the thickest.

[0004] Since the thickness of the envelope is non-uniform in the conveyance direction in this way, when a large number of envelopes are loaded, the uppermost surface of the load becomes inclined and does not become horizontal. For this reason, the contact pressure with the sheet feeding belt or the sheet feeding roller becomes unstable, and double feeding or non-feeding jams are likely to occur in the sheet feeding belt or the sheet feeding roller. In particular, when a bundle of envelopes is set in a large sheet feeding device (LCIT), the non-uniformity in thickness accumulates in the uppermost layer of the bundle of envelopes, and the contact pressure with the sheet feeding belt or the sheet feeding roller becomes even more unstable, and double feeding or non-feeding jams are even more likely to occur. Therefore, the invention of Patent Document 2 arranges an auxiliary bottom plate biased upward by a spring opposite to the sheet feeding roller to stabilize the contact pressure of the sheet feeding roller.

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if the auxiliary bottom plate is arranged to be vertically movable, the sheet feeding device becomes structurally complex and the number of components increases. Therefore, an object of the present invention is to provide a sheet feeding device with a simple structure that can smoothly feed sheets of paper with uneven thickness such as envelopes.

Means for Solving the Problem

[0006] To solve the above problems, the sheet feeding device of the present invention includes a paper stacking part that can be lifted and lowered by a lifting means in a state where a stack of sheets is loaded, a reference fence arranged adjacent to the paper stacking part along the lifting direction of the paper stacking part, which regulates the front end position of the stack of sheets, an end fence arranged opposite to the reference fence with the stack of sheets interposed therebetween, which regulates the rear end position of the stack of sheets, an extrusion means arranged at the upper end of the end fence, which extrudes the uppermost sheet of the stack of sheets in the conveying direction, and a conveying means that contacts the uppermost layer of the stack of sheets loaded on the paper stacking part and conveys the sheets one by one from the reference fence to the downstream side. The sheet feeding device is characterized in that a second stacking part is formed to extend downstream from the upper end of the reference fence by a predetermined length and face the conveying means, and the uppermost sheet extruded onto the second stacking part by the extrusion means is conveyed downstream one by one by the conveying means.

Effect of the Invention

[0007] According to the sheet feeding device of the present invention, sheets of paper with uneven thickness can be smoothly fed with a simple structure.

Brief Description of the Drawings

[0008]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 2C

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description thereof will be simplified or omitted as appropriate. ● Schematic Configuration of Image Forming Apparatus FIG. 1A shows the overall configuration of the image forming apparatus 1 according to the present embodiment. 1 is a copying machine as an image forming apparatus, 2 is an original reading unit that optically reads the image information of the original D, and 3 is an exposure unit that irradiates the exposure light L based on the image information read by the original reading unit 2 onto the photosensitive drum 5.

[0010] 4 is an image forming unit that forms a toner image (image) on the photoreceptor drum 5, 7 is a transfer roller that contacts the photoreceptor drum 5 via the transfer conveyance belt 8 to form a transfer nip, 8 is a transfer conveyance belt that transfers and conveys the toner image formed on the photoreceptor drum 5 to the paper P, 10 is a document conveyance unit (automatic document feeder) that conveys the set document D to the document reading unit 2. Also, 12, 13 are paper feed cassettes (paper feeding devices) in which the paper P is stored, 17 is a registration roller (timing roller) that conveys the paper P toward the transfer nip.

[0011] Further, 20 is a fixing device that fixes the toner image (unfixed image) carried on the paper P, 21 is a fixing roller installed in the fixing device 20, 22 is a pressure roller installed in the fixing device 20, 31 is a paper discharge tray on which the paper P discharged from the apparatus main body 1 is stacked, 70 is a sheet feeding device (high-capacity feeding device) that stores a bundle EB of a large amount of paper (or envelopes, etc.), 100 is an operation panel on which operation buttons for displaying various information in the apparatus and performing operations are displayed.

[0012] ●Operation of the image forming apparatus Next, the operation during normal image formation by the image forming apparatus 1 will be described. First, the document D is conveyed (fed) from the document table in the direction of the arrow in the figure by the conveyance rollers of the document conveyance unit 10 and passes over the document reading unit 2.

[0013] At this time, in the document reading unit 2, the image information of the document D passing above is optically read. Then, the optical image information read by the document reading unit 2 is converted into an electrical signal and then transmitted to the exposure unit 3 (writing unit). And from the exposure unit 3, exposure light L such as laser light based on the image information of the electrical signal is emitted toward the photoreceptor drum 5 of the image forming unit 4.

[0014] On one hand, in the image forming section 4, the photosensitive drum 5 rotates in the clockwise direction shown in Fig. 1A. After undergoing a predetermined image forming process (charging process, exposure process, development process), an image (toner image) corresponding to the image information is formed on the photosensitive drum 5. Then, the image formed on the photosensitive drum 5 is transferred onto the paper P conveyed by the resist roller 17 at the transfer nip (the position where the transfer roller 7 contacts the photosensitive drum 5 via the transfer conveyance belt 8).

[0015] On the other hand, the paper P conveyed to the transfer nip operates as follows. First, one of the plurality of paper feed cassettes 12 and 13 of the image forming apparatus main body 1 is selected automatically or manually (for example, assume that the uppermost paper feed cassette 12 is selected).

[0016] Then, the topmost sheet of the paper P stored in the paper feed cassette 12 is fed by the paper feed mechanism 52 (which is composed of a feed roller, a pickup roller, a backup roller, etc.) and conveyed toward the conveyance path. After that, the paper P passes through the conveyance path where a plurality of conveyance rollers are arranged and reaches the position of the resist roller 17.

[0017] When the large-capacity sheet feeding device 70 (large-capacity feeding device) installed on the side of the apparatus main body 1 is selected, among the plurality of sheets, envelopes, etc. stacked on the paper stacking section 72 (see Fig. 2) of the sheet feeding device 70, the topmost sheet, envelope, etc. are fed by the conveyance belt 91 (see Fig. 1B) of the conveyance device 90 toward the conveyance path where the conveyance roller 55 is installed. The said sheet, envelope, etc. will then reach the position of the resist roller 17.

[0018] The paper that has reached the position of the resist roller 17 is conveyed toward the transfer nip while synchronizing the timing to align with the image formed on the photosensitive drum 5. After passing through the position of the transfer nip, the paper after the transfer process is conveyed by the transfer conveyance belt 8 and reaches the fixing device 20.

[0019] The sheet that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 22, and the toner image is fixed by the heat received from the fixing roller 21 and the pressure received from both members 21 and 22 (this is the fixing process). After the fixing process in which the toner image is fixed, the sheet is discharged from between the fixing roller 21 and the pressure roller 22 (this is the fixing nip), and then discharged from the image forming apparatus main body 1 and stacked on the paper discharge tray 31 as an output image. Thus, a series of image forming processes is completed.

[0020] Next, the sheet feeding device 70 (high-capacity feeding device) in the present embodiment will be described in detail. Referring to FIG. 1B, the sheet feeding device 70 is for feeding sheets in a predetermined feeding direction (the direction of the arrow in FIG. 1B), and is composed of a sheet storage unit 71, a conveying device 90, air blowing devices 76 and 79, etc. The sheet storage unit 71 is composed of a sheet stacking unit 72 (bottom plate), a reference fence 73, a regulating plate 80, an end fence 74, a side fence 75, etc.

[0021] The conveying device 90 is composed of a conveying belt 91 as a conveying means stretched and supported by two roller members (a driving roller 93 and a driven roller 92), a suction device 95 (belt suction device), etc. Then, the sheets accommodated in the sheet storage unit 71 are conveyed in the feeding direction indicated by the arrow in FIG. 1B by the conveying device 90.

[0022] The reference fence 73 is formed so as to stand vertically upward on the downstream side in the conveying direction of the sheet storage unit 71 (sheet stacking unit 72). The sheet stacking unit 72 is formed so that a plurality of sheets can be stacked in contact with the reference fence 73.

[0023] Further, the paper stacking unit 72 is configured to be able to move up and down such that the height-direction position of the topmost sheet of paper, regardless of the number of sheets of paper stacked, becomes a predetermined height position detected by the paper detection sensor. That is, the paper stacking unit 72 is for stacking a plurality of sheets of paper, and according to the height (number of stacked sheets) of the stacked paper, it moves up and down along the reference fence 73 by the elevating mechanism in the vertical direction (the direction of the white double arrow in FIG. 1B).

[0024] The elevating mechanism for moving the paper stacking unit 72 up and down is composed of an elevating motor, pulleys, a timing belt, wires, a fixed pulley, etc. When the elevating motor is rotationally driven in the forward direction (clockwise direction) under the control of the control unit, the drive is transmitted to the pulley via the timing belt, and the wire wound around the fixed pulley by the pulley is wound up by the winding unit, and the paper stacking unit 72 rises. On the contrary, when the elevating motor is rotationally driven in the reverse direction (counterclockwise direction) under the control of the control unit, the drive is transmitted to the pulley via the timing belt, and the winding of the wire is released by the pulley, and the paper stacking unit 72 descends.

[0025] Here, the sheet feeding device 70 (high-volume feeding device) in the present embodiment is configured to be able to stack a large amount of paper of a predetermined size (for example, A4 vertical size) that is frequently used by the user. The end fence 74 has its position in the feeding direction (the distance from the reference fence 73) determined according to the size of the paper in the feeding direction (the left-right direction in FIG. 1B).

[0026] Similarly, the pair of side fences 75 have their intervals in the width direction determined according to the size of the paper in the width direction (the direction orthogonal to the feeding direction, which is the direction perpendicular to the paper surface in FIG. 1B). The side fence 75 is provided with a side blowing device 76 (first blowing means) that blows air from the side toward the topmost sheet of paper stacked on the paper stacking unit 72 in synchronization with the blowing timing of the front blowing device 79 described later to lift the sheet.

[0027] This side air blower 76 is configured in substantially the same manner as the front air blower 79, except for the different installation positions. The user places the held paper (paper stack) on the installation space on the paper loading unit 72 (a space surrounded on four sides by the reference fence 73, a pair of side fences 75, and the end fence 74) so as to abut against the reference fence 73, and the setting of the paper (paper stack) into the paper storage unit 71 is completed.

[0028] Note that a regulating plate 80 is installed at the upper part of the reference fence 73 in the paper storage unit 71. The regulating plate 80 is installed so as to stand up upward from the reference fence 73. This regulating plate 80 regulates the movement in the feeding direction of the lower papers other than the uppermost paper lifted by the air blowers 76 and 79.

[0029] The regulating plate 80 is for preventing the problem that the lower papers not scheduled to be adsorbed and conveyed by the conveying belt 91 are fed (double-fed) together with the uppermost paper scheduled to be adsorbed and conveyed by the conveying belt 91. Specifically, when the lower papers are likely to be double-fed, the papers interfere with the regulating plate 80, and their movement (feeding) in the conveying direction is restricted.

[0030] As shown in FIG. 1B, the front air blower 79 is installed on the downstream side in the feeding direction (the left side in FIG. 1B) with respect to the paper loading unit 72 (paper storage unit 71). The front air blower 79 blows air toward the paper placed on the paper loading unit 72 to lift the paper.

[0031] When the uppermost paper is separated by the front air blower 79 and lifted upward, suction is performed by the suction device 95 above the air blower 79, so the adsorption of the uppermost paper toward the conveying belt 91 is promoted. Note that the timing at which the front air blower 79 ejects air toward the uppermost paper is preferably the same timing as when the suction operation by the suction device 95 starts, or a timing slightly earlier than that.

[0032] In this way, the front blower 79 blows air from the downstream side in the paper feeding direction toward the paper placed on the paper loading unit 72 to lift the paper. On the other hand, the side blower 76 as the first blowing means blows air from the widthwise end side toward the paper placed on the paper loading unit 72 to lift the paper.

[0033] The suction device 95 is installed above the paper loading unit 72 (paper storage unit 71). The suction device 95 is for sucking the paper lifted by the blowers 76 and 79. Specifically, the suction device 95 generates a negative pressure of air above the plurality of papers stacked on the paper loading unit 72 to suck the topmost paper.

[0034] Specifically, the suction device 95 is composed of a suction fan, a suction duct, a suction chamber, etc. The suction chamber is installed inside the conveyor belt 91, and the opening formed at the bottom thereof is formed to communicate with the lower space through a plurality of small-diameter hole portions formed in the conveyor belt 91, and the hole portion formed at one end side in the width direction is connected to the suction fan through the suction duct. Then, when the suction fan operates, air is sucked from the bottom of the conveyor belt 91 in the direction of the white arrow in FIG. 1B.

[0035] The conveying device 90 conveys the paper (the topmost paper) adsorbed on the conveyor belt 91 in the paper feeding direction by the suction of the suction device 95. Specifically, the conveyor belt 91 is installed at the most downstream side in the paper feeding direction above the paper storage unit 71 and straddles the discharge port of the sheet feeding device 70.

[0036] The conveyor belt 91 is stretched and supported by two roller members 92 and 93, and the driving roller 93 is rotationally driven by a driving motor to rotate (travel) in the clockwise direction in FIG. 1B. A plurality of small-diameter hole portions are formed over the entire surface of the conveyor belt 91.

[0037] ● The second loading unit of the sheet feeding device As shown in FIGS. 2A and 2B, the sheet feeding device 70 of this embodiment has a second stacking portion (73a, 73b, 73c). This second stacking portion extends substantially horizontally with a predetermined length L from the upper end portion of the reference fence 73 toward the downstream side.

[0038] Further, the second stacking portion extends in a direction perpendicular to the paper surfaces of FIGS. 2A and 2B and is capable of accommodating (receiving) sheets of the maximum width. The central portion in the longitudinal direction of the second stacking portion is the horizontal portion 73a, and this horizontal portion 73a faces the conveying belt 91 as a conveying means in the vertical direction.

[0039] The state when a small amount of envelope bundles are stacked on the sheet stacking portion 72 can be reproduced by the second stacking portion. Therefore, the horizontal level of the uppermost stacking surface can be maintained without worrying about the inclination (deviation) of the uppermost stacking surface when a large amount of envelope bundles are stacked on the sheet stacking portion 72.

[0040] For this reason, it becomes possible to stabilize the contact pressure of the pickup roller 55c and feed the sheets stably. The movement of the second stacking portion by the blowing of the pushing air can also be performed smoothly.

[0041] Inclined portions 73b and 73c continue to the downstream side and the upstream side of the horizontal portion 73a. The downstream inclined portion 73b is continuous with the horizontal guide plate G, and the upstream inclined portion 73c is continuous with the upper end portion of the reference fence 73. These inclined portions 73b and 73c smooth the horizontal leftward movement of the envelope bundle EB.

[0042] The length L of the second stacking portion (73a, 73b, 73c) is preferably formed longer than the conveyance direction length E1 of the flap portion that closes the opening of the envelope (E1 < L). That is, when the sheets stacked on the sheet stacking portion 72 in FIG. 2A are envelopes with different thicknesses on the front end side and the rear end side, the flap portion that closes the opening of the envelope is arranged on the rear end side. For this reason, a flap sag surface is formed as shown in FIG. 2A.

[0043] Due to this drooping flap surface, the flap portion is likely to develop a bending habit of curling downward. Therefore, if the length L of the second loading portion (73a, 73b, 73c) is shorter than the length E1 of the flap portion, the correction of the bending habit of the flap portion will be insufficient, and double feeding or non-feeding jams are likely to occur with the conveyor belt 91 or the conveyor roller 55.

[0044] ● Second air blowing means An air blower 82 is disposed at the upper end of the end fence 74. This air blower 82 constitutes a second air blowing means for blowing extrusion air toward the rear end portion of the uppermost layer of the envelope bundle EB.

[0045] By the extrusion air from the air blower 82, the downstream end of the uppermost layer of the envelope bundle EB is extruded onto the second loading portion (73a, 73b, 73c). At this time, the movement of the envelope bundle EB is smoothed by the inclined portions 73b, 73c.

[0046] The conveyor belt 91 as a conveying means can be replaced with a pickup roller 55c as shown in FIG. 2C. In this case, the pickup roller 55c and the horizontal portion 73a of the second loading portion face each other in the vertical direction.

[0047] ● Conventional sheet feeding device As shown in FIG. 3A, the conventional sheet feeding device 70 has no second loading portion, and the pickup roller 55c and the guide plate G face each other in the vertical direction. Therefore, the uppermost layer of the envelope bundle EB pushed out from the reference fence 73 to the downstream side comes into contact with the pickup roller 55c immediately.

[0048] As shown in FIG. 3B, the thickness of the envelope E is such that the flap portion E1 at the downstream end in the conveying direction is the thinnest (single layer). The main body portion E2 in the middle of the conveying direction has a thickness twice that of the flap portion E1, and the pasted side E3 at the upstream end in the conveying direction has a thickness three times that of the flap portion E1. Therefore, the thickness increases in the order of flap portion E1 < main body portion E2 < pasted side E3.

[0049] Therefore, when the bundle of envelopes EB is loaded on the paper loading unit 72, as shown in FIG. 3A, a flap sag occurs at the flap portion E1 at the upstream end in the transport direction. Then, when the topmost envelope is transported downstream by the pickup roller 55c, the flap portion E1 with a curled bend on the lower side contacts the pickup roller 55c as it is, and the contact pressure at this time suddenly increases due to the upward bounce of the flap portion E1. This sudden increase in the contact pressure makes it easy for double feeding or non-feeding jams of the envelopes to occur in the pickup roller 55c.

[0050] The invention of Patent Document 2 disposes an auxiliary bottom plate 85 biased upward by a spring 86 opposite to the pickup roller 55c as shown in FIG. 4. On the other hand, a push-out member 74a is disposed at the upper end of the end fence 74 so as to be movable back and forth. When the topmost layer of the bundle of envelopes EB is pushed out downstream in the transport direction by the push-out member 74a, the topmost envelopes E come into contact with the pickup roller 55c one by one and are transported downstream.

[0051] In the transport of the topmost envelope E, even if the flap portion E1 approaches the pickup roller 55c and tries to bounce upward, the auxiliary bottom plate 85 absorbs the upward bounce of the flap portion E1 to stabilize the contact pressure with the pickup roller 55c. However, if the auxiliary bottom plate 85 is disposed so as to be vertically movable, the sheet feeding device 70 becomes structurally complicated and the number of parts also increases.

[0052] ● Baffle plate FIGS. 5A and 5B show an embodiment in which a baffle plate 87 that can protrude and retract with respect to the upper surface of the guide plate G is disposed. When the transport roller 55 is composed of a feed roller 55a, a retard roller 55b, and a pickup roller 55c as the transport means, when the topmost layer of the bundle of envelopes EB is transported downstream by the push-out air of the blower device 82, the topmost sheet may go too far and enter unexpectedly downstream of the pickup roller 55c. When the sheet goes too far like this, it leads to double feeding or non-feeding jams of the sheet.

[0053] Therefore, in FIGS. 5A and 5B, a blocking plate 87 is disposed between the pickup roller 55c and the guide plate G so as to be vertically movable. The blocking plate 87 extends in a direction perpendicular to the paper surfaces of FIGS. 5A and 5B with a predetermined length, and in a state of protruding from the upper surface of the guide plate G as shown in FIG. 5A, it prevents the uppermost layer of the envelope bundle EB from entering the downstream side of the pickup roller 55c.

[0054] When the pickup roller 55c moves downward and contacts the guide plate G as shown in FIG. 5B during paper feeding, the blocking plate 87 moves downward in conjunction with the pickup roller 55c and is accommodated below the guide plate G. Therefore, the pickup roller 55c can contact a predetermined position of the leading edge of the paper on the guide plate G to perform stable paper feeding.

[0055] ● Suction air and separation air The adhesion between papers varies depending on the paper type, paper thickness of the paper, and the usage environment of the sheet feeding device 70. For this reason, it is assumed that the papers cannot be moved only by the pushing air on the rear end side.

[0056] Therefore, in this embodiment, the suction air in FIG. 6 and the separation air in FIG. 7 are used as necessary. When pushing the uppermost layer of the envelope bundle EB to the downstream side with the pushing air, the possibility of the envelope bundle EB being double-fed is reduced by the suction air and the separation air.

[0057] FIG. 6 shows an embodiment in which a suction device 84 is disposed below the second stacking portion, and the suction air is applied to the downstream end of the second stacking portion by this suction device 84. By slightly sucking the leading edge of the paper with the suction air during paper conveyance, slippage (double-feed) of the leading edge of the paper can be prevented.

[0058] ● First blowing means FIG. 7 shows an embodiment in which separation air is blown out from the outside of the side fence by a blower device 76 (first blowing means). This separation air is blown onto both the left and right sides of the uppermost layer of the envelope bundle EB through the duct 76a.

[0059] Separation air can reduce the adhesion of the top sheet of the envelope bundle EB and cause the sheets to spread out. Therefore, it becomes easier to move the sheets downstream.

[0060] ● Pressing member FIG. 8 shows an embodiment in which a pressing member 88 is fixedly disposed at the upper end of the end fence 74. This pressing member 88 has an inclined surface for inclining the rear end portion of the top layer of the envelope bundle EB upward forward.

[0061] When the blowing air is blown out from the blower 82 while raising the sheet loading portion 72, the rear end portion of the top layer of the envelope bundle EB comes into contact with the pressing member 88 and becomes inclined upward forward. As a result, the front end portion of the top layer of the envelope bundle EB can easily ride on the second loading portion, and in combination with the second loading portion, the contact pressure between the top layer of the envelope bundle EB and the pickup roller 55c can be stabilized.

[0062] Conventionally, as shown in FIG. 4, a configuration in which a pushing member 74a is disposed at the upper end of the end fence 74 so as to be movable back and forth is known. However, if the pushing member 74a is configured to be movable, the structure becomes complicated and the number of parts increases. By fixedly disposing the pressing member 88 as in the present embodiment, the structure can be simplified and the number of parts can be reduced.

[0063] As described above, the present invention has been specifically described based on the embodiments. However, it goes without saying that the present invention is not limited to the above embodiments and can be variously modified within the scope of the technical idea described in the claims. For example, the present invention is not limited to the large-capacity sheet feeding device 70, and can also be applied to the small-capacity paper feed cassettes 12 and 13 as shown in FIG. 1A.

[0064] ● Supplementary note Hereinafter, preferred embodiments of the present invention will be appended. <First aspect> The first aspect is a sheet feeding device having a paper stacking unit that can be lifted by lifting means in a state where a stack of sheets is loaded, a reference fence disposed adjacent to the paper stacking unit along the lifting direction of the paper stacking unit and regulating the front end position of the stack of sheets, an end fence disposed opposite to the reference fence with the stack of sheets interposed therebetween and regulating the rear end position of the stack of sheets, pushing means disposed at the upper end of the end fence and pushing out the uppermost sheet of the stack of sheets in the conveying direction, and conveying means that contacts the uppermost layer of the stack of sheets loaded on the paper stacking unit and conveys the sheets one by one from the reference fence to the downstream side. The sheet feeding device forms a second stacking unit that extends downstream from the upper end of the reference fence by a predetermined length and faces the conveying means, and conveys the uppermost sheet pushed out to the second stacking unit by the pushing means downstream one by one by the conveying means. <Second Aspect> The second aspect is the sheet feeding device according to the first aspect, characterized in that when the sheet is an envelope with different thicknesses on the front end side and the rear end side, the length of the second stacking unit is longer than the conveying direction length of the flap portion that closes the opening of the envelope. <Third Aspect> The third aspect is the sheet feeding device according to the first or second aspect, characterized in that a guide plate for guiding the lower surface of the sheet is disposed downstream of the second stacking unit, and a blocking plate is disposed so as to be able to protrude and retract with respect to the upper surface of the guide plate. <Fourth Aspect> The fourth aspect is the sheet feeding device according to any one of the first to third aspects, characterized in that suction means for sucking the front end of the sheet with suction air is disposed downstream of the second stacking unit, and when the sheet is conveyed downstream by the conveying means, the front end of the sheet is sucked by the suction air of the suction means. <Fifth Aspect> The fifth aspect is the sheet feeding device according to any one of the first to fourth aspects, characterized in that first blowing means for blowing separation air for separating the uppermost sheet of the stack of sheets in the left-right direction of the stack of sheets is disposed when the sheet is conveyed downstream by the conveying means. <Sixth Aspect> In the sixth aspect, when the paper is conveyed downstream by the conveying means, the extrusion means includes a second air blowing means for blowing extrusion air from the upper end of the end fence, and / or a pressing member disposed at the upper end of the end fence for pressing the rear end of the paper bundle to incline it forward. The sheet feeding device according to any one of the first aspect to the fifth aspect is characterized by this. That is. <Seventh Aspect> The seventh aspect is an image forming apparatus characterized by including the sheet feeding device according to any one of the first aspect to the fifth aspect.

Explanation of Reference Numerals

[0065] 1: Image forming apparatus 2: Document reading unit 3: Exposure unit 4: Image forming unit 5: Photoconductor drum 7: Transfer nip 8: Transfer conveyance belt 10: Document conveyance unit 12, 13: Paper feed cassette 17: Registration roller 20: Fixing device 21: Fixing roller 22: Pressing roller 31: Paper discharge tray 52: Paper feeding mechanism 55: Conveying roller 55a: Feed roller 55b: Retard roller 55c: Pickup roller 71: Paper storage unit 72: Paper stacking unit 73: Reference fence 73a: Horizontal part (second stacking part) 73b, 73c: Inclined part (second stacking part) 74: End fence 74a: Extrusion member 75: Side fence 76: Air blowing device (first air blowing means) 79: Front air blowing device 80: Regulation plate 82: Air blowing device (second air blowing means) 84: Suction device 85: Auxiliary bottom plate 86: Spring 87: Baffle plate 88: Pressing member 90: Conveying device 91: Conveying belt 92: Driven roller 93: Driving roller 95: Suction device D: Original manuscript E: Envelope E1: Flap part E2: Main body part E3: Gluing side EB: Bundle of envelopes EB: Bundle of envelopes G: Guide plate L: Exposure light P: Paper

Prior art documents

Patent documents

[0066]

Patent Document 1

Patent Document 2

Claims

1. A paper stacking unit that can be raised and lowered by raising and lowering means in a state where a stack of sheets is loaded, A reference fence disposed along the raising and lowering direction of the paper stacking unit at a position adjacent to the paper stacking unit, for regulating the front end position of the stack of sheets, An end fence disposed opposite to the reference fence with the stack of sheets interposed therebetween, for regulating the rear end position of the stack of sheets, Pushing means disposed at the upper end of the end fence for pushing out the uppermost sheet of the stack of sheets in the conveying direction, A sheet feeding device having conveying means that contacts the uppermost layer of the stack of sheets loaded on the paper stacking unit and conveys the sheets one by one from the reference fence to the downstream side, Forming a second stacking unit that extends downstream from the upper end of the reference fence by a predetermined length and faces the conveying means, The sheet feeding device is characterized in that the uppermost sheet pushed out to the second stacking unit by the pushing means is conveyed downstream one by one by the conveying means.

2. The sheet feeding device according to claim 1, characterized in that when the sheet is an envelope with different thicknesses on the front end side and the rear end side, the length of the second stacking unit is longer than the conveying direction length of the flap portion that closes the opening of the envelope.

3. The sheet feeding device according to claim 1, characterized in that a guide plate for guiding the lower surface of the sheet is disposed downstream of the second stacking unit, and a stopper plate is disposed so as to be able to protrude and retract with respect to the upper surface of the guide plate.

4. The sheet feeding device according to claim 1, characterized in that suction means for sucking the front end portion of the sheet with suction air is disposed downstream of the second stacking unit, and when the sheet is conveyed downstream by the conveying means, the front end portion of the sheet is sucked by the suction air of the suction means.

5. The sheet feeding device according to claim 1, characterized in that first blowing means for blowing separation air for separating the uppermost sheet of the stack of sheets in the left-right direction of the stack of sheets is disposed when the sheet is conveyed downstream by the conveying means.

6. When the pushing means conveys the sheet downstream by the conveying means, Second blowing means for blowing pushing air from the upper end of the end fence, and / or A pressing member disposed at the upper end of the end fence for pressing the rear end portion of the stack of sheets and tilting it forward, The sheet feeding device according to claim 1, characterized by having.

7. An image forming apparatus, characterized by having the sheet feeding device according to any one of claims 1 to 6.

Images