The present application claims priority to and incorporates by reference the entire contents of Japanese priority document 2008-032229 filed in Japan on Feb. 13, 2008.
1. Field of the Invention
The present invention relates to a sheet creaser, a sheet conveyer including a conveying path on which the sheet creaser is provided, a sheet finisher including the sheet creaser, an image forming apparatus including the sheet finisher or the sheet finisher.
2. Description of the Related Art
In the field of image forming apparatuses such as inkjet printers, electrophotographic copiers, facsimile machines, and multifunction products (MFPs), sheet finishers that receive a set of sheet-like recording mediums (hereinafter, “sheets”) from an image forming apparatus and perform post-processing such as stapling have been widely used. With the development of multi-functional-sheet finishers, sheet finishers with both a side-stitch function and a saddle-stitch function have appeared. In most of the sheet finishers with the saddle-stitch function, a folding unit that folds the set of sheets includes at least one pair of rollers called pressure rollers and a plate member called folding plate. More particularly, the folding plate is aligned with a line to be folded of the set of sheets, and inserts the set of sheets into a nip between the pressure rollers. Thus, a crease is made along the line to be folded on the set of sheets with the nip.
Some folding units include a first pair of pressure rollers and a second pair of pressure rollers. The set of sheets is pressed twice with the first pressure rollers and the second pressure rollers, which makes a stronger crease.
However, even when the set of sheets is pressed twice, it is difficult to make a crease strong enough due to a short pressing time and a low pressing force. Because a rotation axis of the pressure rollers runs parallel to a direction perpendicular to a sheet conveying direction, a folded side of the set of sheets is pressed in the nip between the pressure rollers only for a short time. Moreover, because the pressure rollers nip the entire folded side at the same time, the pressing force on the set of sheets is distributed, i.e., the pressing force per unit area is low.
There has been disclosed a technology for making a stronger crease, in which a slide-pressing unit re-presses the folded side while sliding in a direction perpendicular to the sheet conveying direction.
Japanese Patent Application Laid-open No. 2003-341930 discloses a sheet finishing method of accumulating a plurality of sheets received from the image forming apparatus and saddle-stitching/half-folding the sheets. More particularly, after the sheets are saddle-stitched, the stitched sheets are inserted in between a pair of first pressure rollers in such a manner that a center line with respect to the sheet conveying direction is pressed by the folding plate. Thus, a crease is made on the sheets. After that, the crease is re-pressed by a second pressure roller that is sliding in the direction perpendicular to the sheet conveying direction in such a manner that a rotational axis of the second pressure roller is oblique with respect to the crease. Thus, the strong crease is made on the sheets.
In Japanese Patent Application Laid-open No. 2003-341930, a guiding member that is swinging upward guides the second pressure roller so that the second pressure roller moves up slantwise and then moves down onto the crease. The guiding member is swung by a driving force of a motor.
In a typical sheet creaser that makes the strong crease by re-pressing the folded side of the sheets with a slidable pressure roller, such as the second pressure roller disclosed in Japanese Patent Application Laid-open No. 2003-341930, sliding in the direction perpendicular to the sheet conveying direction, if the folded side of the sheets is thick, a load on the motor steeply increases when the slidable pressure roller slides up on the crease. This may results in a step-out of the motor.
In Japanese Patent Application Laid-open No. 2003-341930, the increase in load on the motor when the second pressure roller slides up on the crease is suppressed by the presence of the guiding member. However, if the size of sheets is variable, the guiding member has to move in the sheet-width direction to near the corner of the current sheets. That is, it is necessary to provide a moving space extending in the sheet-width direction. Moreover, it is necessary to provide a driving unit that moves the guiding member. This brings an increase of costs and an increase of necessary space for the driving unit. Because a typical driving unit includes a motor and a driving-force transmission mechanism, it is expected to bring a large increase in the number of parts and a large increase in the necessary space.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to one aspect of the present invention, there is provided a sheet creaser including a pressing unit that presses a folded side of a stack of sheets folded by a folding unit, thereby making a strong crease on the stack of sheets, which includes a pressure roller that slides on the folded side while rotating, an elastic biasing unit that presses the pressure roller in a thickness direction of the stack of sheets, and a driving unit that slides the pressure roller in a direction substantially perpendicular to a conveying direction of the stack of sheets; and a lifting unit that, when the pressure roller slides to a first position, temporarily lifts up the pressure roller, and when lifted-up pressure roller slides to a second position, lifts the lifted-up pressure roller down onto the folded side. The first position and the second position are located before a corner of the folded side, whereby the pressure roller cannot slide up on the folded side.
Furthermore, according to another aspect of the present invention, there is provided a method of creasing sheets in a sheet creaser including a pressing unit that presses a folded side of a stack of sheets folded by a folding unit, thereby making a strong crease on the stack of sheets. The pressing unit includes a pressure roller that slides on the folded side while rotating, an elastic biasing unit that presses the pressure roller in a thickness direction of the stack of sheets, and a driving unit that slides the pressure roller in a direction substantially perpendicular to a conveying direction of the stack of sheets. The method includes first lifting including temporarily lifting up, when the pressure roller slides to a first position, the pressure roller; second lifting including lifting down, when lifted-up pressure roller slides to a second position, the lifted-up pressure roller onto the folded side, wherein the first position and the second position are located before a corner of the folded side, whereby the pressure roller cannot slide up on the folded side; sliding, after the pressure roller is lifted down onto the folded side, the pressure roller that is pressed by an elastic force of the elastic biasing unit back and forth along the folded side.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings.
The sheet finisher PD is attached to a side of the image forming apparatus PR. A sheet ejected from the image forming apparatus PR is conveyed to the sheet finisher PD. The sheet passes through a conveyer path A for single-sheet processing (e.g., a punching unit 100 is located near the conveyer path A). After that, the sheet is conveyed by the operation of switching claws 15 and 16 to any one of a conveyer path B connecting to an upper tray 201, a conveyer path C connecting to a shift tray 202, a conveyer path D connecting to a side-stitch tray F for alignment and stapling. The image forming apparatus PR includes, although not shown in the drawings, an image processing circuit for converting received image data into printable image data, an optical writing device that writes a latent image with a light on a photosensitive element based on an image signal received from the image processing circuit, a developing device that develops the latent image to a toner image, a transferring device that transfers the toner image onto a sheet, and a fixing device that fixes the tonner image on the sheet. The image forming apparatus PR sends the sheet with the fixed toner image to the sheet finisher PD. Upon receiving the sheet from the image forming apparatus PR, the sheet finisher PD performs a certain post-processing with the sheet. Although the above explanation is made assuming that the image forming apparatus PR is an electrophotographic machine, the image forming apparatus PR can be any type of image forming apparatus such as an inkjet machine or a thermal-transfer machine.
After the alignment and stapling is performed at the side-stitch tray F with the sheet that has been passed through the conveyer paths A and D, the sheet is conveyed by the operation of a guiding member 44 to either the conveyer path C connecting to the shift tray 202 or a saddle-stitch tray G for saddle-stitch and folding. If the sheet is conveyed to the saddle-stitch tray G, the sheet is folded or the like at the saddle-stitch tray G. The folded sheet is conveyed to a conveyer path H and ejected onto a lower tray 203. The conveyer path D is provided with a switching claw 17 that keeps a position as shown in
An entrance sensor 301 that detects the sheet coming from the image forming apparatus PR, a pair of entrance rollers 1, the punching unit 100, a punch-waste hopper 101, a pair of conveyer rollers 2, and the switching claws 15 and 16 are arranged near the conveyer path A in this order, with the entrance sensor 301 being closest to the image forming apparatus PR. The switching claws 15 and 16 keep positions as shown in
When the sheet is to be conveyed to the conveyer path B, the solenoids are kept OFF, and thereby the switching claws 15 and 16 are in the positions shown in
The sheet finisher PD can perform various sheet processing including punching using the punching unit 100, alignment and side stitch using a pair of jogger fences 53 and a side-stitch stapler S1, alignment and saddle stitch using an upper saddle-stitch jogger fence 250a, a lower saddle-stitch jogger fence 250b, and a saddle-stitch stapler S2, sorting using the shift tray 202, half-folding using a folding plate 74 and a pair of first pressure rollers 81. Moreover, the sheet finisher PD can perform slide-pressing using a slide-pressing unit 525 (see
As show in
The reverse roller 13 is made of sponge. When the sheet is ejected by the ejection rollers 6, the reverse roller 13 comes in contact with the sheet so that the back end of the sheet abuts against an end fence, which makes the sheets stacked on the shift tray 202 aligned. The reverse roller 13 rotates by the rotation of the ejection rollers 6. There is a lift-up stop switch (not shown) near the reverse roller 13. When the shift tray 202 lifts up and pushes the reverse roller 13 up, the lift-up stop switch turns ON and a shift-tray lifting motor (not shown) stops. Thus, the shift tray 202 cannot move up beyond a predetermined position.
The sheet sensor 330 is arranged near the reverse roller 13. The sheet sensor 330 detects a position of the top one out of sheets stacked on the shift tray 202. When it is determined using the sheet sensor 330 that the position of the top sheet reaches a predetermined height, the shift tray 202 moves down by a predetermined amount by the action of the shift-tray lifting motor so that the position of the top sheet is always at the same level.
The ejection rollers 6 are formed with a driving roller 6a and a driven roller 6b. The driven roller 6b is arranged upstream of the driving roller 6a, and is rotatably attached to a free end of an open/close guiding plate. The open/close guiding plate is attached to the sheet finisher PD rotatably around the other end, arranged with the free end being closer to the shift tray 202. The driven roller 6b comes in contact with the driving roller 6a under the weight of the driven roller 6b or by a biasing force, and the sheet is ejected through between the driving roller 6a and the driven roller 6b. When stapled sheets are to be ejected, the open/close guiding plate moves up to a predetermined position, and then moves down at predetermined timing decided based on a detection signal from an ejection sensor 303. The predetermined position is decided based on a detection signal from a guiding-plate open/close sensor (not shown). The open/close guiding plate moves up, driven by a guiding-plate open/close motor (not shown).
When the sheet is conveyed to the side-stitch tray F by the rotation of the stapled-sheet conveyer rollers 11, the sheet is stacked on the side-stitch tray F. More particularly, the sheet goes backward by rotation of a reverse roller 12 in the vertical direction (i.e., the sheet conveying direction), and abut against an end fence 51, which makes the sheets stacked on the side-stitch tray F aligned. A direction perpendicular to the sheet conveying direction (i.e., the sheet-width direction) is aligned with the jogger fences 53. When it is determined based on a staple signal from a control circuit 350 that a last one of a set of sheets is stacked on the side-stitch tray F, the side-stitch stapler S1 stapes the set of sheets. A sheet pressing member 110 presses a side of the set of sheets when the side-stitch stapler S1 staples the sheets.
A home position (HP) of a lifting claw 52a is detected with an ejection-belt HP sensor 311. The ejection-belt HP sensor 311 turns ON/OFF by operation of the lifting claw 52a attached to a lifting belt 52. Two lifting claws 52a are attached to an outer surface of the lifting belt 52, with the lifting claws 52a being opposed to each other. The two lifting claws 52a alternately lift the set of sheets out of the side-stitch tray F.
The lifting belt 52 rotates between a driving pulley and a driven pulley along a center line of the aligned sheet width. A plurality of lifting rollers 56 are attached rotatably to a driving shaft, working as driven rollers. The lifting rollers 56 are arranged symmetric to each other with respect to the lifting belt 52.
The reverse roller 12 swings around a fulcrum 12a by a tapping solenoid, which causes the back end of the sheets stacked on the side-stitch tray F to abut against the end fence 51. The reverse roller 12 rotates counterclockwise. The pair of jogger fences 53 is arranged so that both width-direction sides of the stacked sheets put between them. The jogger fences 53 slide in the sheet-width direction back and forth via a timing belt (not shown) by positive-driving or negative-driving of a jogger motor (not shown). The side-stitch stapler S1 moves to a target position in the sheet-width direction via a timing belt (not shown) by positive-driving or negative-driving of a stapler moving motor (not shown) to staple the target position of the sheet side.
A saddle-stitch mechanism related to the slide-pressing process is explained below. A side-stitch mechanism is not explained, because the side-stitch mechanism is not a feature of the sheet finisher PD.
It is assumed that the sheet is conveyed to the conveyer path D by the operation of the switching claws 15 and 16, and then is conveyed to the side-stitch tray F by the operation of the conveyer rollers 7, 9, and 10, and the stapled-sheet conveyer rollers 11. At the side-stitch tray F, the sheet is aligned with the stapled-sheet conveyer rollers 11 both in the saddle-stitch mode and the side-stitch mode (see
After a set of sheets (hereinafter, “stack of sheets 603”) is roughly aligned at the side-stitch tray F, the stack of sheets 603 is lifted up with the lifting claw 52a. As shown in
In the saddle-stitch tray G, the stack of sheets 603 is conveyed with a pair of upper conveyer rollers 71 and a pair of lower conveyer rollers 72 (72a, 72b) to a position at which the front end of the stack of sheets 603 abuts against a movable backend fence 73 as shown in
The stack of sheets 603, the movable backend fence 73, and the relative members shown in
As shown in
As shown in
A slidable pressure roller 600 and a mechanism for driving the slidable pressure roller 600 are not shown in
The CPU 360 controls those components by reading program codes from a read only memory (ROM) (not shown), loading the program codes on a work area of a random access memory (RAM) (not shown), and executing the loaded program codes.
The slide mechanism includes a holder 601, a first guiding member 602, a spring 609, a first slider 608, a first sliding shaft 607, a first stepping motor 612, a first pulley 605, and a first timing belt 606.
The slidable pressure roller 600 is fit in the holder 601 in such a manner the slidable pressure roller 600 is rotatably attached to a spindle 601a of the holder 601. Thus, the slidable pressure roller 600 slides while rotating. The first guiding member 602 is attached, as a projection, to a side face of the holder 601 that faces opposite to the sheet conveying direction. The holder 601 is suspended from the first slider 608 via a shaft. Due to an elastic force of the spring 609 between the holder 601 and the first slider 608, the holder 601 is movable up and down. The spring 609 is a so-called compression spring. The holder 601 and the slidable pressure roller 600 are always pressed against a guiding plate 613 that forms a part of the sheet conveyer path by the elastic force of the spring 609.
The first slider 608 is slidably attached to the first sliding shaft 607 to slide in the direction perpendicular to the sheet conveying direction. The first slider 608 is fixed to the first timing belt 606 that is located above the first sliding shaft 607. The first timing belt 606 is stretched between a pulley 612a and the first pulley 605. The pulley 612a is a driving pulley and the first pulley 605 is a driven pulley. The pulley 612a is provided to a driving shaft of the first stepping motor 612. With this configuration, the first slider 608 slides back and forth along the first sliding shaft 607 by the rotation of the first timing belt 606.
A first light sensor 604 is provided near an end of the first sliding shaft 607. Assume now that the first light sensor 604 is provided near the end of the first sliding shaft 607 close to the first pulley 605 as shown in
The second sliding shaft 616 runs parallel to the first sliding shaft 607, i.e., in the direction perpendicular to the sheet conveying direction. The second guiding member 611 is slidably attached to the second sliding shaft 616 to slide in the direction perpendicular to the sheet conveying direction. The second guiding member 611 is fixed to the second timing belt 617 that is located above the second sliding shaft 616. The second timing belt 617 is stretched between a pulley 619a and the second pulley 618. The pulley 619a is a driving pulley and the second pulley 618 is a driven pulley and. The pulley 619a is provided to a driving shaft of the second stepping motor 619. With this configuration, the second guiding member 611 slides back and forth along the second sliding shaft 616 by the rotation of the second timing belt 617.
The second guiding member 611 is located upstream of the sheet with respect to the sliding direction of the first slider 608. The second guiding member 611 is arranged so that a lower surface 602a of the first guiding member 602 slides, accompanied by the sliding of the first slider 608, on an upper surface 611a of the second guiding member 611. The lower surface 602a and the upper surface 611a make a cam mechanism. That is, when the lower surface 602a slides on the upper surface 611a, the slidable pressure roller 600 moves up above the sheet surface in the presence of the elastic force of the spring 609 nevertheless, and then moves down onto the sheet surface. More particularly, the slidable pressure roller 600 is moved up before reaching a left side 603b of the stack of sheets 603, and then moved down on the left side 603b. The positions where the slidable pressure roller 600 is moved up and down depend on shape and position of the second guiding member 611.
With this configuration, the slide-pressing mechanism operates as follows from the initial state shown in
The angle of slope of the upper surface 611a is relatively small so that the slidable pressure roller 600 moves to a level above the folded side 603a of the stack of sheets 603 with a relatively small change in load when the first guiding member 602 slides on the second guiding member 611. Therefore, no trouble occurs such as the step-out of the first stepping motor 612.
It is necessary to move, based on sheet-size data received from the image forming apparatus, the second guiding member 611 to a position outside of the sheet width, and stand-by the second guiding member 611 at that position. This is because it is necessary to temporarily move up the slidable pressure roller 600 so as to fall the slidable pressure roller 600 down onto the folded side 603a. The second guiding member 611 is, as described above, fixed to the second timing belt 617 and moved accompanied by the rotation of the second timing belt 617. The second timing belt 617 is rotated by the driving force of the second stepping motor 619 via the second pulley 618. A shielding plate 615 is attached to the second guiding member 611 as a projection so that the shielding plate 615 shields a second light sensor 614 when the second guiding member 611 is in the HP. The distance from the HP is measured by using a pulse of the second light sensor 614. If the sheet width is small, the second guiding member 611 moves from the position as shown in
After acquiring the sheet-width data, the second guiding member 611 is moved to the stand-by position by the driving force of the second stepping motor 619 (Step S103). The stand-by position of the second guiding member 611 is set to a position L1 mm away from the HP shown in
The slidable pressure roller 600 is slid back and forth on the folded side 603a by the driving force of the first stepping motor 612 (Step S107). More particularly, the slidable pressure roller 600 moves from the position shown in
The slidable pressure roller 600 slides back from the position shown in
In this manner, as described with reference to
The sheet creaser incorporated in the sheet finisher is described in the embodiment. However, the sheet creaser capable of the slide-pressing can be incorporated in a sheet conveyer, an image forming apparatus, an image forming system, or the like from viewpoints of space savings. If the sheet creaser is incorporated in the sheet conveyer, the sheet creaser is, for example, placed upstream of a cutting device that cuts the stack of sheets 603.
The embodiment of the present invention brings various effects as follows.
Firstly, the slidable pressure roller 600 gradually moves up and then gradually moves down onto the folded side 603a instead of sliding up on the folded side 603a, which suppresses an amount of increase in the load on the first stepping motor 612 that drives the slidable pressure roller 600. Therefore, a step-out of the first stepping motor 612 is prevented.
Secondly, if the sheet width is variable, the second guiding member 611 moves to the stand-by position corresponding to the current sheet width so that the slidable pressure roller 600 moves down onto the folded side 603a without sliding up on the corner of the stack of sheets 603. In other words, it is possible to deal with the variable sheet size with the simple configuration requiring a relatively small space.
Thirdly, the slidable pressure roller 600 gradually moves up and then gradually moves down onto the folded side 603a instead of sliding up on the folded side 603a. Thus, no tear is made on the corner of the stack of sheets 603.
According to an aspect of the present invention, it is possible to provide a small-space low-cost sheet creaser capable of making a strong crease with preventing a step-out of a motor.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
Number | Date | Country | Kind |
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2008-032229 | Feb 2008 | JP | national |