Patent Application
20110233853
Embodiments described herein relate generally to a sheet stacking apparatus, a sheet finishing apparatus, an image forming apparatus and a sheet stacking method.
An image forming apparatus generally has functions to forma latent image by selectively exposing the surface of a photoconductive drum, to develop the latent image by a developer or the like to obtain a visible image, and to transfer it to a sheet to obtain a copy. Although no limitation is made to the image forming apparatus as stated above, a sheet copied by a copying machine is finally stacked on a discharge tray. The discharge tray may be provided as a sheet stacking apparatus separate from the image forming apparatus, or may be provided integrally with the image forming apparatus. When the number of sheets to be copied is small, a fixed tray may be used.
However, when the number of copied sheets is large, the amount of sheets stacked on the discharge tray increases. Then, in order to stably hold the stacked sheets, a movable tray capable of moving up and down is used in many cases, and the movable tray is lowered and sheets are stacked. The design can be made such that also when the number of sheets is small, they are discharged to the movable tray.
An apparatus is known in which when the stack amount increases, an angle of the movable tray is tilted more than usual to stably secure sheets.
However, even if the angle of the tray is changed, when the stack amount is large, the sheets can not be stably aligned and secured.
The invention provides a sheet stacking apparatus capable of aligning and stacking sheets even when the sheet stack amount increases.
According to an embodiment of the invention, a sheet stacking apparatus includes a movable tray having a sheet stack part whose center part is dented downward as the number of discharged and stacked sheets increases, and a movement control mechanism part to move and control the movable tray up and down.
Hereinafter, embodiments of the invention will be described with reference to the drawings. In the following, a description is made on the assumption that an image forming apparatus including the sheet stacking apparatus of the embodiments is a multi-function type color copying apparatus.
The operation keys 7 of the operation panel 5 include, for example, a numeric keypad, a reset key, a stop key, a start key and the like. The display part 6 gives various instructions of, for example, sheet size, the number of copies, print density setting and the like.
The image reading part 2 includes a document table 8, a carriage 9, an exposure lamp 10, a reflecting mirror 11, an imaging lens 12 and a CCD (Charge Coupled Device) 13. The CCD 13 is a photoelectric conversion element to capture reflected light and converts it into an electric signal. An auto document feeder 30 to convey a document to a read position is provided above the document table 8.
The image forming part 4 includes an intermediate transfer belt 14 as a transfer body, and four process units 16Y, 16M, 16C and 16K arranged side by side along the intermediate transfer belt 14 and corresponding to toners (recording materials) of respective colors of yellow (Y), magenta (M), cyan (C) and black (K). Since these process units have the same structures, the black process unit is typically selected here and this will be described.
The process unit 16K includes a photoreceptor 18K as an image carrier, a laser unit 20K to form an electrostatic latent image on the photoreceptor 18K, a charging device 22K disposed around the photoreceptor 18K, a developing device 24K, a primary transfer device 26K opposite to the photoreceptor 18K through the intermediate transfer belt 14, a cleaner 27K and a charge removing lamp 28K.
The operation of the process unit 16K will be described. First, a document is placed on the document table 8 or the auto document feeder 30 conveys a document to a read position. Next, the exposure lamp 10 supported by the carriage 9 irradiates light to the document from beneath the document table 8. An image of reflected light from the document is focused and is projected onto the CCD 13.
The CCD 13 captures the reflected light and outputs image information of the document as an analog signal. The electric signal transmitted by the CCD 13 is converted into a digital signal. The laser unit 20K receives the digital signal subjected to image processing.
When the image forming part 4 starts image formation, the charging device 22K charges the outer peripheral surface of the rotating photoreceptor 18K. The laser unit 20K irradiates a laser beam in accordance with the digital signal subjected to the image processing to the outer peripheral surface of the photoreceptor 18K charged to a uniform potential in the axial direction by the charging device 22K in order to form an electrostatic latent image.
The developing device 24K supplies a black developer (for example, toner) to the outer peripheral surface of the photoreceptor 18K, and develops the electrostatic latent image with the toner. The primary transfer device 26K electrostatically transfers the toner image to the intermediate transfer belt 14.
The cleaner 27K disposed downstream of the primary transfer device 26K in the rotation direction of the photoreceptor 18K removes the toner remaining on the photoreceptor 18K without being transferred. The charge removing lamp 28K disposed downstream of the cleaner 27 in the rotation direction of the photoreceptor 18K removes the remaining charge on the outer peripheral surface of the photoreceptor 18K. In the color image formation, the process units 16Y, 16M and 16C similarly perform the above operation.
A secondary transfer device 36 electrostatically transfers the toner image transferred on the intermediate transfer belt 14 to a sheet conveyed from a sheet feed device 32 through a conveyance path 34. A fixing device 38 fixes the toner image to the sheet. A conveyance roller 40 conveys the sheet on which the toner image is fixed to a branch member 42. The transfer device and the fixing device constitute a print part of the sheet.
The branch member 42 guides the sheet to a reverse roller 44 or a conveyance roller 54 based on the sheet processing. When the branch member 42 guides the sheet to the reverse roller 44, the reverse roller 44, a branch member 46 and a conveyance roller 48 convey the sheet to a sheet discharge roller 50, and the sheet discharge roller 50 discharges the sheet to an upper-stage fixed tray 107.
When two-sided printing is performed, the branch member 42 guides the sheet to the reverse roller 44, and the reverse roller 44 is reversely rotated and conveys the sheet to the branch member 42. The branch member 42 guides the sheet to a conveyance roller 56, and the conveyance roller 56 conveys the sheet to the secondary transfer device 36. As a result, the secondary transfer device 36 transfers a toner image to the opposite surface of the conveyed sheet. The fixing device 38 fixes the toner image to the sheet. Besides, for example, when the size of the sheet is, for example, A3 size and is large, the branch member 46 guides the A3 size sheet to a reverse paper path, and the reverse roller 44 is reversely rotated and conveys the A3 size sheet to the branch member 42.
When the branch member 42 guides the sheet to a conveyance roller 60, the conveyance roller 60 conveys the sheet to a carry-out roller 62, and the carry-out roller 62 discharges the sheet to a movable tray 140 of a sheet finishing apparatus 100 as indicated by a dotted line. The movable tray 140 is controlled by a movement control mechanism part 144. The movement control mechanism part 144 includes a tray position detection part 140s to detect the position of the movable tray 140, a tray drive belt 140b, and a tray drive motor 140m to drive and control the rotation of the tray drive belt 140b.
Incidentally, the sheet here is, for example, standard thick paper, thin paper, glossy paper, OHP sheet or the like.
The sheet finishing apparatus 100 processes the sheet discharged from the image forming apparatus 1 in accordance with input instructions from the operation panel 5 or instructions from a separately connected PC.
The sheet finishing apparatus 100 includes an inlet roller 102, a branch member 104, a sheet discharge roller 106, an exit roller 108, a standby tray 110, a standby roller 112, a processing tray 114, an alignment member 116, a stapler 118, a sheet bundle discharge member 120, the fixed tray 107, the movable tray 140 and a shutter 160.
The inlet roller 102 receives the sheet on which the image is formed by the image forming apparatus 1, and conveys it to the branch member 104. The branch member 104 guides the sheet to the sheet discharge roller 106 or the exit roller 108.
The branch member 104 discharges the sheet to the fixed tray 107. On the other hand, when the branch member 104 guides the sheet to the exit roller 108, the exit roller 108 conveys the sheet to the standby tray 110. The standby tray 110 temporarily holds plural conveyed sheets. After supporting a predetermined number of sheets, the standby tray 110 drops the supported sheets to the processing tray 114.
When after-mentioned lateral alignment or stapling is not performed using the processing tray 114, the standby tray 110 conveys the supported sheets directly in the direction of the movable tray 140, and discharges them. In this case, the standby tray 110 and the standby roller 112 do not stop the sheets at the standby tray 110, and discharges the sheets one by one to the movable tray 140.
When the lateral alignment or stapling is performed, the following operation is performed. The processing tray 114 receives the sheets dropped by the standby tray 110. While the sheets are aligned or stapled, the processing tray 114 supports the stacked sheets. The alignment member 116 aligns a sheet bundle on the processing tray 114 in the lateral direction crossing the conveyance direction. The stapler 118 staples the end of the aligned sheet bundle as the need arises. The sheet bundle discharge member 120 discharges the stapled sheet bundle to the movable tray 140.
The movable tray 140 is controlled by the movement control mechanism part 144 including the tray drive belt 140b and the tray drive motor 140m, and moves up and down. A detection member 132 detects the upper surface of the movable tray 140 or the uppermost surface of the sheets stacked on the movable tray 140. The detection member 132 is attached to the shutter 160.
For example, when one or plural sheets are discharged, the movable tray 140 is controlled by the movement control mechanism part 144, and moves downward. The stacked sheets are removed from the movable tray 140, and when a sheet on the movable tray 140 is not detected, the movable tray 140 is controlled by the movement control mechanism part 144, and moves upward. The movable tray 140 moves to the position where the detection member 132 detects the uppermost surface of sheets stacked on the movable tray 140, and stacks discharged sheets.
The movable tray 140 includes a sheet stack part 141 for stacking a discharged sheet.
As shown in
Accordingly, when the number of sheets stacked on the sheet stack part 141 of the movable tray 140 is small, as shown in
Accordingly, as the number of discharged sheets increases, and the stack amount becomes high, a V-shaped recess becomes deep by the mechanical operation due to the difference in the elastic force of the pressure springs. Incidentally, since the position of the sheet discharge port is fixed, in general, when the sheet stack amount increases, in order to stack the sheets, the movable tray 140 is positioned downward as indicated by an arrow 149 in
Although a sheet freely drops from the sheet discharge port to the sheet stack part, when the stack amount increases, the center part is dented and the sheet can be certainly stacked.
Next, a second embodiment of a sheet stacking apparatus will be described with reference to
Also in this embodiment, as shown in
In the sheet stacking apparatus of this embodiment, as the weight of sheets stacked on the two plates increases, the force of pulling by the electromagnetic solenoids 174a, 174b and 174c is made high.
Accordingly, the boundary portion of the two plates is pulled downward according to the weight of the sheets stacked on the sheet stack part 141, the V shape is formed in the direction vertical to the sheet discharge direction, and a large number of sheets can be certainly stacked on the sheet stack part 141. Since the height of the sheet discharge port can not be changed, also in this case, in general, as the number of stacked sheets increases, the movable tray 140 is positioned below as indicated by an arrow 179.
Incidentally, in the second embodiment, the sheet detection part 177 detects the weight of the sheets stacked on the sheet stack part 141, and the degree of pulling by the electromagnetic solenoids 174a, 174b and 174c is changed according to the weight. However, information of the thickness of the stacked sheets detected by the sheet thickness sensor 176 is directly inputted to the solenoid drive part 178, and as the thickness of the sheets becomes large, the pulling force (attracting force) by the electromagnetic solenoids 174a, 174b and 174c is made high, and the V shape of the two plates can be formed.
Besides, the weight of the stacked sheets is directly measured without measuring the thickness of the stacked sheets, and the solenoid drive part 178 may drive and control the electromagnetic solenoids 174a, 174b and 174c.
In the second embodiment, as the thickness of the sheets stacked on the sheet stack part 141 increases, the degree of pulling by the electromagnetic solenoids is made high. However, the electromagnetic solenoids are not driven until the thickness of the stacked sheets becomes a predetermined thickness, and when the thickness becomes the predetermined thickness, the electromagnetic solenoids may be driven, so that the section of the two plates becomes V-shaped.
The predetermined thickness at which the electromagnetic solenoids are driven may be divided into two or more stages.
Since the height of the sheet discharge port through which the sheet enters the sheet stacking apparatus can not be changed, in general, as the number of stacked sheets increases, the movable tray is positioned downward. Accordingly, the height position of the movable tray is detected, and according to this, the V shape formed of two plates of the sheet stack part can be changed. A description will be made on a third embodiment in which the V shape of the sheet stack part of the movable tray is changed according to the position of the movable tray as stated above. In this embodiment, the shapes of two plates are deformed by a cam mechanism.
The position detection part 196 detects the position of the rotation shaft 194, and detects the positions of the two plates 192a and 192b and the holding body 193. When the number of sheets stacked on the two plates 192a and 192b increases, the rotation belts 198a and 198b are rotated and driven by a not-shown motor or the like, and the holding body 193 and the like are lowered as indicated by an arrow A. The position detection part 196 detects the lowering of the position, and the rotation shaft 194 is rotated. When the rotation shaft 194 is rotated, the eccentric cams 195a and 195b fixed to the rotation shaft 194 are rotated, and raise portions of the plates 192a and 192b farther from the boundary upward as indicated by arrows 199a and 199b.
Accordingly, the shape formed of the two plates 192a and 192b becomes V-shaped in the direction vertical to the sheet discharge direction, and as the sheet stack amount increases, the depth of the V shape becomes deep.
In the invention, the degree of denting of the center of the sheet stack part may be gradually changed to form the V shape according to the amount, such as thickness or weight, of stacked sheets, that is, may be changed in analog, or may be changed digitally to increase the dent amount stepwise when the sheet amount reaches a certain amount. The invention includes both the cases.
The sheet stacking apparatus of the embodiment of the invention may be included in the finishing apparatus, or may be provided integrally with the image forming apparatus.
In the embodiment, the description is made on the case where the invention is applied to the multi-function type color copying apparatus. However, the invention can be applied to not only the multi-function type color copying apparatus, but also a sheet stacking apparatus for stacking a sheet discharged by another image forming apparatus, such as a normal copying machine, a printer or a facsimile, which includes an image forming part to generate an image to be printed on a sheet and specifies the type of a print sheet.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and sprit of the inventions.
This application is based upon and claims the benefit of priority from U.S. provisional Application Ser. No. 61/318255 filed on Mar. 26, 2010. The entire contents of the provisional application are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61318255 | Mar 2010 | US |
