US20090121421A1

US20090121421A1 - Post-processing apparatus and image forming system

Info

Publication number: US20090121421A1
Application number: US12/266,302
Authority: US
Inventors: Junichi Fujita; Hisao Hosoya; Hiroto Ito; Kenji Kawatsu
Original assignee: Konica Minolta Business Technologies Inc
Current assignee: Konica Minolta Business Technologies Inc
Priority date: 2007-11-12
Filing date: 2008-11-06
Publication date: 2009-05-14
Also published as: JP5023979B2; JP2009120272A

Abstract

A post-processing apparatus having therein a stacker that stocks sheets temporarily and an ejection device that ejects a plurality of sheets stacked on the stacker from the stacker wherein the ejection device has an ejection claw that pushes up the plural sheets and a moving device that moves the ejection claw along the stacker, the ejection claw has a contact surface with which the aforesaid plural sheets are brought into contact when the plural sheets are pushed up, and the contact surface has plural protrusions protruding toward the plural sheets.

Description

This application is based on Japanese Patent Application No. 2007-293003 filed on Nov. 12, 2007 in Japanese Patent Office, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a post-processing apparatus having therein a stacker that stocks sheets temporarily and an ejection device that ejects a plurality of sheets stacked on the stacker and to an image forming system having therein the post-processing apparatus.
There is known a post-processing apparatus wherein plural image-recorded sheets ejected from an image forming apparatus are collected in the form of a group of plural sheets to be outputted, or sheets are collated for each copy and stapled by a stapler to be outputted.
It is further known that a period of time required for post-processing such as stapler processing in a post-processing apparatus is generally longer than a period of time required for image forming processing in an image forming apparatus.
Therefore, there is known a post-processing apparatus wherein a stacker that stocks sheets temporarily is provided in the post-processing apparatus to stack a prescribed number of sheets.
As the post-processing apparatus of this kind, there is known an apparatus wherein an ejection device that ejects stacked plural sheets to an ejection tray and a stapler representing a post-processing apparatus is provided, and plural sheets are pushed up and ejected by an ejection claw fixed on the ejection device (for example, Unexamined Japanese Patent Application Publication No. 8-137151).
In the post-processing apparatus described in Unexamined Japanese Patent Application Publication No. 8-137151, it is possible to eject plural sheets (sheet bundle) to an ejection tray or to a stapler, by pushing up plural sheets with an ejection claw provided on the ejection device
However, with respect to a shape of the ejection claw, its contact surface with a sheet is flat, excluding a protrusion on the uppermost section, as illustrated in FIG. 1 (a). Therefore, in the case of a poor fragile sheet or a curled sheet, in particular, the contact portion side of the sheet contacting the ejection claw tends to be shifted toward a tip portion of the ejection claw when a sheet bundle is pushed up, and if it is shifted greatly, there is a possibility that the contact portion side of the sheet contacting the ejection claw climbs over the protrusion on the uppermost section, causing conveyance abnormality, which has been a problem.
Further, for example, when an ejection claw is arranged only at a position corresponding to the width direction of a small-sized sheet, if a large-sized sheet is tried to be ejected out, resistance of conveyance is increased by curls on the end portion of the large-sized sheet bundle, and the sheet is easily skewed. If the sheet is skewed, there is a possibility that the contact portion side of the sheet contacting the ejection claw climbs over the protrusion on the uppermost section, causing conveyance abnormality, which has been a problem.
The followings are aspects of the invention.
1. A post-processing apparatus comprising: a stacker which stocks a sheet temporarily; and an ejection device which ejects a plurality of sheets from the stacker on which the plurality of sheets have been stacked, the ejection device comprising: an ejection claw which pushes up the plurality of sheets; and a moving device which moves the ejection claw along the stacker, wherein the ejection claw comprises a contact surface with which the plurality of sheets are brought into contact when the ejection claw moves and pushes up the plurality of sheets by the moving device, and the contact surface comprises a plurality of protrusions which protrudes toward the plurality of sheets stacked on the stacker.
2. An image forming system having therein an image forming apparatus that conducts image forming on a sheet and a post-processing apparatus described in the aforesaid Item 1 connected to the image forming apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (a) is a conceptual diagram describing a stacker and an ejection device in a conventional embodiment and FIG. 1 (b) is one in a present embodiment.

FIG. 2 is a diagram showing a post-processing apparatus and an image forming system equipped with the post-processing apparatus.

FIGS. 3 (a) and 3 (b) are schematic diagrams showing sheet conveyance courses including the first conveyance path and the second conveyance path.

FIG. 4 is a schematic diagram showing a sheet conveyance course using the third conveyance path.

Each of FIGS. 5 (a) and 5 (b) is a detailed diagram of an ejection claw fixed on an ejection belt.

Each of FIGS. 6 (a) and 6 (b) is a diagram of another embodiment for a protrusion provided on an ejection claw.

FIG. 7 is a diagram of the fourth embodiment for a protrusion provided on an ejection claw.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Prior to the detailed description of the embodiment, outlines of the present embodiment and of the conventional embodiment will be described as follows, for easy understanding of the description.
FIGS. 1 (a) and 1 (b) are conceptual diagrams describing a stacker and an ejection device in a conventional embodiment and those in a present embodiment.
FIG. 1 (a) is a conceptual diagram describing a conventional stacker and a conventional ejection device, while, FIG. 1 (b) is a conceptual diagram describing a stacker and an ejection device both in the present embodiment.
In FIG. 1 (a), stacker 101 that stacks plural sheets temporarily has stopper 103 that conducts alignment on the conveyance direction side for sheets fed from the preceding process, whereby, plural sheets are stacked while alignment of sheets on the conveyance direction side is conducted (two-dot chain lines).
Ejection device 102 that ejects a bundle of sheets (two-dot chain lines) stacked on stacker 101 has ejection claw 104 that pushes up bundle of sheets P1 (solid lines) in the direction of the arrow to eject them toward the succeeding progress.
Contact surface 105 of ejection claw 104 with which a bundle of sheets is brought into contact is flat, and tip portion 106 of the ejection claw is slightly protrudent in the pushing up direction.
The ejection claw 104 has no measures to prevent a bundle of sheets from being shifted on contact surface 105 undesirably toward tip portion 106, and only measures to prevent a bundle of sheets from protruding from ejection claw 104 are represented by tip portion 106 that is slightly protrudent in the pushing up direction.
For this reason, when the bundle of sheets is pushed up in the direction of the arrow, its portion on the side of contact with ejection claw 104 tends to be bent, as illustrated, and in the case of a non-rigid sheet or in the case of existence of a curl, in particular, there is a possibility that the bundle of sheets is shifted undesirably on the contact surface 105, and it runs on protrusion 107 on the tip portion.
The foregoing means that the force toward protrusion 107 of a tip portion by own weight of a bundle of sheets overcomes frictional force between the bundle of sheets and contact surface 105, thus, the bundle of sheets is shifted to the protrusion 107 side.
As a result, when the bundle of sheets runs on the protrusion 107 of the tip portion, there is caused conveyance abnormality which has been a cause for the decline of reliability and productivity.
In FIG. 1 (b), stacker 111 that stacks plural sheets temporarily has stopper 113 that conducts alignment on the conveyance direction side for sheets fed from the preceding process, whereby, plural sheets are stacked while alignment of sheets on the conveyance direction side is conducted (two-dot chain lines).
Ejection device 112 that ejects plural sheets (two-dot chain lines) stacked on stacker 111 from stacker 111 by pushing up them has ejection claw 114 that pushes up plural sheets, namely, bundle of sheets P1 (solid lines) in the direction of the arrow to eject them toward the succeeding progress, and has ejection belt 56 that is a moving device to move the ejection claw 114 in the direction for pushing up along stacker 111.
Contact surface 115 of ejection claw 114 touched by the bundle of sheets has protrusions 118, and tip portion 116 of ejection claw 114 forms protrusion 117 that is taller than the protrusions 118 in the direction (direction of the arrow) for pushing up.
Owing to this, although bundle of sheets P1 tends to be bent when it is pushed up, a contact side of the sheet contacting ejection claw 114 (hereafter, a contact side of the sheet contacting ejection claw 114 is described as a trailing edge of the sheet) is caught by protrusions 118. Therefore, the trailing edge of a sheet is restrained from sliding on contact surface 115 and from being moved toward protrusion 117, even in the case of existence of curls, in particular, thus, the bundle of sheets P1 is prevented from being bent greatly.
Therefore, the bundle of sheets P1 can be prevented from running on protrusion 117 of the aforesaid tip portion.
In other words, the bundle of sheets P1 is caused to be caught by the contact surface 115 thereon, and thereby, a trailing edge of the bundle of sheets P1 is prevented from being shifted toward the protrusion 117, without relying on frictional force between the bundle of sheets P1 and the contact surface 115 thereon as in the past.
Owing to this, no conveyance abnormality is caused, and reliability and productivity are improved.
Referring to the drawings, embodiments will be described as follows, to which, however, the invention is not limited.
Incidentally, devices and members having the same functions and forms as those in other drawings are given the same symbols as those in other drawings.
FIG. 2 is a diagram showing a post-processing apparatus and an image forming system equipped with the post-processing apparatus.
Image forming system Z has therein image forming apparatus A that records an image on a sheet and a post-processing apparatus B that conducts post-processing on the sheet on which the image is recorded by the image forming apparatus A.
First, the image forming apparatus A will be described.
The image forming apparatus A is one (for example, a copying machine, a printer and a facsimile machine) that forms an image on a sheet through an electrophotographic method, and it has image forming section A1, document feeding device A2 and image reading section A3.
Start-up of the image forming apparatus A starts document feeding device A2 to operate.
The document feeding device A2 conveys documents to a reading position one after another.
Then, the image reading section A3 reads a document conveyed by the document feeding device A2 or an image of a document placed on document table 9, and generates image signals.
Around drum-shaped photoreceptor 1 in the image forming section A1, there are arranged charging unit 2 that charges photoreceptor 1 uniformly, exposure unit 3 that gives exposure based on the aforesaid image signals of an image of the document, developing unit 4 that visualizes a latent image resulted from exposure by using toner, transfer unit 5A that transfers a toner image formed on the photoreceptor onto a sheet, separation unit 5B that separates a sheet from photoreceptor 1, and cleaning unit 6 that removes toner remaining on photoreceptor 1, whereby, images are formed on sheet S by these units of electrophotographic process.
Sheet S is stored in sheet feed tray 7A, and sheet S is fed from sheet feed tray 7A one by one, and a toner image on photoreceptor 1 is transferred onto sheet S by transfer unit 5A.
Then, the toner image transferred onto sheet S passes through fixing unit 8 to be subjected to fixing processing.
Then, the sheet S which has been subjected to the fixing processing is ejected to post-processing apparatus B from sheet ejection roller 7C.
In the case of two-sided image forming, the sheet S is guided downward by switching gate 7D, and it passes through sheet re-feed path 7E after being reversed inside out by a switchback, to be fed to transfer unit 5A again where an image on the reverse side is transferred.
Operation panel P representing a selection device for selecting operations of post-processing conducted by post-processing apparatus B has a touch panel (not shown), and it displays various selection switches and information relating to operations of post-processing on the touch panel.
For example, selection switches for sizes of sheets to be used such as A4 and B4 and selection switches for operations of post-processing such as, for example, sheet stacking processing and staple processing, are displayed.
Then, various pieces of information from operations of various types of selection switches are inputted in control device C1.
Each of the image forming apparatus A and the post-processing apparatus B has an information sending and receiving device that sends and receives post-processing operation information selected by the aforesaid post-processing operation selecting switch that is a selection device which selects operations of post-processing to be conducted in the post-processing apparatus.
Communication device C11 of image forming apparatus A conducting serial communication and communication device C21 of post-processing apparatus B, both representing an information sending and receiving device send and receive various types of information relating to operations of post-processing each other.
Control device C1 controls the aforesaid operations relating to the image forming apparatus A.
Post-processing apparatus B will be described as follows.
The post-processing apparatus B is an apparatus for conducting various types of post-processing including staple processing on sheet S fed in from the image forming apparatus A.
The post-processing apparatus B is installed after its position and height are adjusted so that an entrance portion for sheet S may agree with an ejecting direction of ejection roller 7C of image forming apparatus A, and the post-processing apparatus B is driven in accordance with operations of the image forming apparatus A.
A conveyance path for sheet S that is connected to the downstream side of the sheet conveyance direction of paired entrance rollers 11 in the aforesaid entrance portion is branched into three ways including first conveyance path 100 on the upper portion, second conveyance path 200 on the medium portion and third conveyance path 300 on the lower portion.
Then, sheet S is fed to any one of the conveyance paths through the selection of an angle of each of switching gates G1, G2 and G3.
The first conveyance path 100 causes sheet S to be ejected and stacked on sheet ejection tray 19 located at an upper portion outside the apparatus.
Through the second conveyance path 200, sheet S is ejected and stacked on sheet ejection tray 40 by paired ejection rollers 20.
On the third conveyance path 300, there are provided stacker 51 that stocks temporarily sheet S and ejection device 60 that pushes up plural sheets stacked on the stacker 51 to eject them from the stacker 51.
The ejection device 60 has therein ejection claw 57 that pushes up plural sheets and ejection belt 56 representing a moving device that moves the ejection claw 57 in the direction to push up the ejection claw 57 along the stacker 51.
A bundle of sheets subjected to stapling processing by stapler 50 after prescribed number of sheets S are stacked on stacker 51, or a bundle of plural sheets collected on the stacker 51 is pushed up by ejection device 60 to be ejected and stacked on sheet ejection tray 40 by paired ejection rollers 20.
Incidentally, the ejection device 60 has a plurality of ejection belts 56, depending on a size of a sheet to be used.
For example, when carrying out post-processing for sheets ranging from B5 to A3 in terms of a size, one ejection belt 56 is provided near each of both ends of a B5 sheet size, for post-processing of B5 and A4 sheet, by which B5 and A4 sheets are pushed up. One ejection belt 56 is provided near each of both ends of a B4 sheet size, for post-processing of B4 and A3 sheet, by which B4 and A3 sheets are pushed up.
Controller C2 controls the aforesaid operations relating to post-processing apparatus B, in accordance with information of operations of post-processing received through communication device C21.
Each of FIGS. 3 (a) and 3 (b) is a schematic diagram showing a sheet conveyance course through the first conveyance path and a sheet conveyance course through the second conveyance path.
FIG. 3 (a) shows a conveyance course (one-dot chain lines) for sheet S through the first conveyance path 100, and FIG. 3 (b) shows a conveyance course (one-dot chain lines) for sheet S through the second conveyance path 200.
(1) First Conveyance Path 100 (Printer Mode, Sheet Ejection with an Image Surface Facing Downward)
In FIG. 3 (a), sheet S ejected from image forming apparatus A with an image surface facing upward (face-up) is conveyed by paired entrance rollers 11, then, passes through passage 121 located at a lower part of upper first switching gate G1, to be interposed between paired conveyance rollers 12, and passes through passage 123 located at an upper part of second switching gate G2 that is positioned downward obliquely.
Then, the sheet S passes through paired conveyance rollers 14, passage 15 and paired conveyance rollers 16 to stop once.
Then, after stopping once, the sheet S is given an operation of a switchback by paired conveyance rollers 12, 14 and 16 which rotate reversely, and passes through passage 122 positioned at an upper part of the first switching gate G1 and passage 17 located higher (first conveyance path 100), and is ejected out by paired ejection rollers 18 onto sheet ejection tray 19 positioned at an upper part outside the apparatus with its image surface facing downward (face-down), to be placed in the order of pages.
(2) Second Conveyance Path 200 (Copy Mode, Sheet Ejection with an Image Surface Facing Upward, Non-Staple Mode Including Offset Ejection)
In FIG. 3 (b), sheet S ejected from image forming apparatus A with an image surface facing upward is conveyed by paired entrance rollers 11, then, passes through passage 121 located at a lower part of upper first switching gate G1.
Then, the sheet S is interposed between paired conveyance rollers 12, and passes through passage 123 located at an upper part of second switching gate G2 that is positioned downward obliquely, and is ejected out with its image surface facing upward to be placed in the order of pages by paired ejection rollers 20 onto sheet ejection tray 40 that is located outside the apparatus.
FIG. 4 is a schematic diagram showing a sheet conveyance course through the third conveyance path.
FIG. 4 shows a conveyance course (one-dot chain lines) for sheet S through the third conveyance path 300.
(3) Third Conveyance Path 300 (Copy Mode, Sheet Ejection with an Image Surface Facing Upward, Staple Mode)
In FIG. 4, sheets S which have been subjected to image forming processing in image forming apparatus A are ejected out in succession with an image surface facing upward, beginning with a copy of the last page.
Sheet S fed into sheet post-processing apparatus B is conveyed by paired entrance rollers 11, and passes through passage 121 located at a lower part of upper first switching gate G1.
Then, the sheet S is interposed between paired conveyance rollers 12, and passes through passage 124 located at an upper part of third switching gate G3 that is positioned downward obliquely, or through lower passage 125, and is fed in stacker 51 through paired conveyance rollers 41, passage 42 (third conveyance path 300) and paired conveyance rollers 43 positioned at the downstream side of the passage 42.
Sheet S interposed between and conveyed by the paired conveyance rollers 43 positioned at the downstream side of the passage 42 is discharged to an upper space of stacker 51 arranged obliquely, and slides and rises further while touching stacker 51 or an upper face of a sheet stacked on the stacker 51.
After sliding and rising, the sheet S starts descending with its own weight, and slides down along an inclined plane of stacker 51 to stop after hitting sheet hitting surface (stopper member) 52 near stapler 50.
Rotary blade wheel 44 that assists the sheet S for sliding down has blades (having no symbol), whereby, when the sheet S is subject to a switchback, rotating blades are brought into sliding contact with the sheet S, so that the sheet S is caused to touch the stopper member 52 surely.
The numeral 53 represents a pair of alignment members provided movably on both sides of the aforesaid stacker 51.
The paired alignment members 53 are movable in the direction perpendicular to the sheet-conveyance direction.
When sheet S is discharged onto stacker 51, the paired alignment members 53 are opened to be broader than a sheet width and when the sheet S slides down along stacker 51 and hits stopper member 52 to stop, the paired alignment members 53 move in the direction of the sheet width on a reciprocation basis, and conduct width aligning (alignment) of a bundle of sheets by tapping a side edge of sheets S.
After sheets S in prescribed quantity are stacked and aligned on stacker 51 at this stopping position, binding processing (staple processing) is conducted by stapler 50 and bundle of stapled sheets S1 is completed.
Even when the staple processing is not conducted, it is also possible to employ constitution wherein plural sheets S are conveyed to stacker 51 for improving accuracy of alignment and, width aligning (alignment) of bundle of sheets S2 stacked simply is conducted by alignment member 53.
On a part in the width direction of a sheet-stacking surface of stacker 51, there is formed a notched portion extending in the direction perpendicular to the width direction, and in this notched portion, there are arranged plural ejection belts 56 each being wound around driving pulley 54 and driven pulley 55, so that the plural ejection belts may be driven to rotate.
On a part of the ejection belt 56, there is fixed ejection claw 57, and a tip portion of the ejection claw 57 moves to draw an oblong locus as shown with illustrated one-dot chain lines.
Bundle of stapled sheets S1 or bundle of plural sheets S2 simply stacked which is placed on the ejection belt 56 slides, with its trailing edge held by ejection claw 57 of ejection belt 56, along a placement surface of stacker 51, to be pushed upward obliquely, and advances to the position of a nip of paired ejection rollers 20.
Bundle of stapled sheets S1 or bundle of plural sheets S2 simply stacked is interposed between rotating paired ejection rollers 20, to be ejected and stacked onto sheet ejection tray 40.
Each of FIGS. 5 (a) and 5 (b) is a detailed diagram of the ejection claw fixed on the ejection belt.
Each of FIGS. 5 (a) and 5 (b) is a sectional view of ejection claw 57 that is viewed in the same direction as in FIG. 4.
FIG. 5 (a) is a detailed diagram of ejection claw 57 and FIG. 5 (b) is a detailed diagram of a protrusion of the ejection claw 57.
The ejection claw 57 and its protrusions will be described as follows, referring to FIG. 5 (a) and FIG. 5 (b).
The ejection claw 57 is moved by ejection belt 56 in the direction of arrow E, when bundle of stapled sheets S1 or bundle of plural sheets S2 simply stacked (hereafter, bundle of stapled sheets S1 or bundle of plural sheets S2 simply stacked is described simply as a bundle of sheets) is ejected.
The ejection claw 57 has therein main body section 58 fixed on ejection belt 56 which is the aforesaid moving device, and sheet contact section 59 that is fixed on the main body section 58 with an adhesive or the like and is in contact with by sheets when bundle of sheets S1 or bundle of sheets S2 is pushed up.
The main body section 58 is formed with a resin which is used usually in a post-processing apparatus, and it is fixed on the ejection belt 56 with screws or an adhesive.
Sheet contact section 59 has, on its sheet contact surface 591, plural protrusions 592 which protrude toward bundle of sheets S1 or bundle of sheets S2.
The protrusions 592 extend in the direction that is parallel to the width direction (the width direction means a direction perpendicular to the sheet-conveyance direction, that is, the illustration sheet front-back direction) of a sheet of a bundle of sheets and protrude toward the bundle of sheets, and for example, they are projections in a rectangular form.
It is preferable that width w1 of the aforesaid projection in a rectangular form (namely, protrusion 592) is about 1 mm, and height h1 is about 0.3 mm.
When the width of the projection is broad, the number of projections is fewer, resulting in fewer portions where sheets are caught. When the width of the projection is narrow, strength of protrusion 592 is lowered.
When the height of the projection is low, a sheet is hardly caught, while, when the projection is tall, accuracy of alignment in the conveyance direction is deteriorated, and a sheet is more easily hurt at the corner of the protrusion.
Further, it is preferable that width w2 of recess 595 between adjoining protrusions is about 2 mm, and when the width is broad, the number of projections is fewer, resulting in fewer portions where sheets are caught. When the width of the projection is narrow, a sheet is hardly caught.
At least surface 593 facing ejection belt 56 among both side faces of the aforesaid rectangular-shaped projection (namely, protrusion 592) is at prescribed angle θ on the bottom plane of recess 595 between adjoining protrusions 592.
It is desirable that the prescribed angle θ is an angle so that the sheet S constituting a bundle of sheets is caught in each protrusion 592, and so that a sheet does not get over each of protrusions 592, which is for example, 80°-95°, preferably 90°.
When the prescribed angle θ is greater than 95°, a sheet is hardly caught by the protrusion 592, and a sheet easily gets over the aforesaid plural protrusions to be shifted toward tip portion 571 of ejection claw 57.
Further, when the prescribed angle θ is smaller than 80°, a sheet tends to cut into the root 592 a of protrusion 592, and scratches or the like tend to be caused on a contacting portion on the sheet when a bundle of sheets is ejected.
A length of the protrusion 592 is extended across the total length in the width direction of ejection claw 57.
The protrusion 592 may be divided in the form of broken lines.
A protrusion located at the uppermost position of the ejection claw 57 among plural protrusions arranged on sheet contact section 59 is taller than other protrusions.
In other words, protrusion 594 that is taller than protrusion 592 is provided on the tip portion 571 side.
The protrusion 594 prevents a bundle of sheets or sheets constituting a bundle of sheets from being protruded from ejection claw 57.
Therefore, it is preferable that height h2 of the protrusion 594 is about 0.4 mm, for example, which is higher than height h1 of protrusion 592.
Protrusion 594 has an angle of about 120° to the bottom plane of recess 595 to prevent protrusion 594 from kicking a trailing edge of a bundle of sheets and from causing damage even when a bundle of sheets is drawn out by paired ejection rollers 20.
In this case, protrusion 594 prevents sheets constituting a bundle of sheets from being protruded from ejection claw 57, because a bundle of sheets is caught mechanically by the protrusion 594.
With respect to sheet contact section 59, it is made of a material having a great friction coefficient, such as, for example, rubber, so that a friction may prevent a bundle of sheets from slipping on sheet contact surface 591 of the sheet contact section 59, in addition to mechanical catching of a bundle of sheets by the aforesaid protrusion 592.
It is also possible to replace only sheet contact section 59 in accordance with a structure of the apparatus, by separating ejection claw 57 into main body section 58 and sheet contact section 59.
Each of FIGS. 6 (a) and 6 (b) is a diagram of another embodiment for the protrusion provided on an ejection claw.
FIG. 6 (a) shows a second embodiment of the protrusion, and FIG. 6 (b) shows a third embodiment of the protrusion.
In FIG. 6 (a), opposite side 598 of surface 593 facing ejection belt 56 of protrusion 596 is cut off obliquely.
Other shapes and dimensions are the same as those of protrusion 592.
By doing this, an angle of the opposite side 598 of surface 593 facing ejection belt 56 can be an obtuse angle that is greater than 90°, which can lighten damage on a portion of the sheet touching sheet contact surface 591.
In FIG. 6 (b), opposite side 599 of surface 593 facing ejection belt 56 of protrusion 597 is cut off to be in the form of a circular arc.
Other shapes and dimensions are the same as those of protrusion 592.
By doing this, an angle of the opposite side 599 of surface 593 facing ejection belt 56 can be a circular arc, which can lighten damage on a portion of the sheet touching sheet contact surface 591.
FIG. 7 is a diagram of the fourth embodiment for a protrusion provided on the ejection claw.
Sheet contact surface 591 of sheet contact section 59 is rough surface 600, except protrusion 594 of tip portion 571.
The rough surface 600 is a finely irregular surface like the form of sandpaper.
Since a sheet is caught by protrusions that form rough surface 600, the sheet is restrained from being shifted on rough surface 600 of ejection claw 57A toward tip portion 571, thus, conveyance abnormality for the sheet can be prevented.
It is preferable that the surface roughness of rough surface 600 is about #80-#180 (Japan Industrial Standards). If the surface is finer than that, a sheet is hardly caught, resulting in difficult control of conveyance abnormality.
If the surface is rougher than that, a contact portion of a sheet that comes in contact with sheet contact surface 591 is damaged.
Though there has been described an occasion where main body section 58 and sheet contact section 59, representing different members from each other, are separated from each other with respect to ejection claw 57, the main body section 58 and the sheet contact section 59 may also be formed unitedly.
In the case of an ejection claw (not shown) wherein main body section 58 and sheet contact section 59 are formed unitedly, plural protrusions being the same as protrusions 592 are provided on a sheet contact surface where a bundle of sheets comes in contact.
Meanwhile, plural protrusions being the same as protrusions 592 restrain a sheet from being shifted on the surface of the ejection claw toward tip portion 571. Therefore, the ejection claw does not always need to be constituted with a material having a high friction coefficient such as a rubber, and it may be constituted with ordinary resin used in a post-processing apparatus.
Owing to this, the number of parts can be reduced, and the number of types of materials to be used can be reduced, resulting in simplification of a manufacturing process and a reduction of manufacturing costs.
By arranging plural ejection claws which push up and eject plural sheets stacked on a stacker that stocks sheets temporarily at positions corresponding to sizes of sheets to be used, and by providing plural protrusions which protrude toward a sheet, on a sheet contact surface of an ejection claw where a sheet comes in contact, it is possible to provide a highly productive post-processing apparatus wherein no conveyance abnormality is caused when ejecting plural sheets in a stacker from the stacker, independently of sheet sizes, and the reliability is improved, then, a production shut-down caused by an interruption with abnormality is lightened, and to provide an image forming system having therein the aforesaid post-processing apparatus.

Claims

1. A post-processing apparatus comprising:

a stacker which stocks a sheet temporarily; and

an ejection device which ejects a plurality of sheets from the stacker on which the plurality of sheets have been stacked,

the ejection device comprising:

an ejection claw which pushes up the plurality of sheets; and

a moving device which moves the ejection claw along the stacker,

wherein the ejection claw comprises a contact surface with which the plurality of sheets are brought into contact when the ejection claw moves and pushes up the plurality of sheets by the moving device, and the contact surface comprises a plurality of protrusions which protrudes toward the plurality of sheets stacked on the stacker.

2. The post-processing apparatus of claim 1,

wherein the plurality of protrusions extend parallel to a width direction of the plurality of sheets stacked on the stacker.

3. The post-processing apparatus of claim 2,

wherein the ejection claw is fixed to the moving device and at least a lateral surface facing the moving device among both lateral surfaces of each of the plurality of protrusions makes a prescribed angle with a bottom surface of a recess between the plurality of protrusions adjacent to each other, the recess being adjacent to the lateral surface.

4. The post-processing apparatus of claim 1,

wherein the ejection device comprises a plurality of the moving devices arranged in a direction perpendicular to an ejection direction of the plurality of sheets stacked on the stacker.

5. The post-processing apparatus of claim 1,

wherein a protrusion positioned at an uppermost portion of the ejection claw among the plurality of protrusions is taller than another protrusion of the plurality of protrusions.

6. An image forming system comprising:

an image forming apparatus which conducts image forming on a sheet; and

a post-processing apparatus of claim 1 connected to the image forming apparatus.

7. The image forming system of claim 6,

wherein the image forming apparatus comprises a selecting device which selects a post-processing operation to be conducted in the post-processing apparatus.

8. The image forming system of claim 7,

wherein each of the image forming apparatus and the post-processing apparatus comprises an information communicating device for communicating information about the post-processing operation selected by the selecting device.