Embodiments described herein relate generally to a sheet folding device which performs folding of printed sheets or the like, an image forming apparatus using this device, and a sheet folding method.
Conventionally, a sheet finisher is known which is installed downstream of an image forming apparatus such as a copier, printer or multi-functional peripheral (MFP) and performs finishing such as punching or stitching of printed sheets.
The functions of the sheet finisher are increasingly diversified. A sheet finisher (middle-folding device) is proposed which has a folding function to fold a part of the sheet and a function of saddle-stitching and middle-folding to staple a central part of the sheet and then fold the sheet at the central part, in addition to the functions of punching and stitching.
In the case of such middle-folding, it is preferable to form a satisfactory fold in order to reduce the thickness of the folded booklet. To this end, it is preferable to nip and fold sheets one by one between a pair of rollers. However, folding sheets one by one in this manner takes time and efficient folding cannot be performed. Meanwhile, when plural sheets are superimposed and folded at a time, efficient folding can be performed. However, it is difficult to form a satisfactory fold on each of the plural sheets.
In view of the foregoing problems of the conventional technique, the invention is to provide a folding device capable of forming a satisfactory fold on each sheet and performing efficiency folding, an image forming apparatus using this device, and a folding method for the same.
According to an embodiment of the invention, a sheet folding device includes a pair of folding rollers which nips a sheet between the folding rollers and thus folds the sheet, a folding blade which pushes the sheet in between the pair of folding rollers, and a folding blade control unit which controls the folding blade to fold a first sheet with the pair of folding rollers, then push a second sheet into the fold of the first sheet, and fold the second sheet with the pair of folding rollers over the first sheet.
Hereinafter, an embodiment of an image forming apparatus and a sheet folding device according to the invention will be described with reference to the drawings.
First, the charger unit 2 uniformly charges the surface of the photoconductive drum 1. Meanwhile, the document read by the reading unit 11 is converted to image data and inputted to the exposure unit 3. The exposure unit 3 casts a laser beam corresponding to the level of the image data to the photoconductive drum 1 and thus forms an electrostatic latent image on the photoconductive drum 1. The electrostatic latent image is developed with a toner supplied from the developing unit 4. A toner image is thus formed on the photoconductive drum 1.
A sheet housed in a sheet housing unit 7A is carried to the space between the photoconductive drum 1 and the transfer unit 5A, which is the transfer position, via several carrying rollers. At the transfer position, the toner image is transferred from the photoconductive drum 1 to the sheet by the transfer unit 5A.
The neutralizing unit 5B erases the electric charges on the surface of the sheet to which the toner image is transferred. The separation pawl 5C separates the sheet from the photoconductive drum 1. After that, the sheet is carried by an intermediate carrying unit 7B. The toner image is then fixed to the sheet by heating and pressurizing by the fixing unit 8. The sheet on which the fixing is finished is discharged from a discharge unit 7C and outputted to the sheet finisher 20.
The cleaning unit 6 arranged downstream of the separation pawl 5C removes the residual developer on the surface of the photoconductive drum 1 and thus the apparatus becomes ready for the next image formation.
In the case of double-side print, the sheet having the toner image fixed to its surface is diverted from the ordinary discharge path by a carrying path switch board 7D and the sides of the sheet are reversed in a switchback-like manner in a reverse carrying path 7E. For the reversed sheet, print similar to single-side print is carried out on the back side and the sheet is outputted from the discharge unit 7C to the sheet finisher 20.
The sheet finisher 20 has a sheet folding device 30 and a sheet placing unit 21, in addition to a sorter unit which sorts the sheet. The sheet folding device 30 folds plural printed sheets discharged from the image forming unit 12, as will be described below. The sheets folded by the sheet folding device 30 are outputted to and placed in the sheet placing unit 21.
The sloped stack tray is seen below the sheet folding device 30. A folding roller pair 38 is provided at the back of a central part of the sheet folding device 30. A folding blade 37 is provided in front of the folding roller pair 38. Stack pawls 211 of stackers 35 are for controlling the position of a sheet, which will be described later, and are controlled to move along apertures 34a and 34b of a stack tray 34 in the direction indicated by double-pointed arrows. The stack tray 34 is provided with a lateral alignment mechanism 40 which laterally aligns a sheet, and a tray sheet detection unit 45 which detects whether there is a sheet on the stack tray 34. The tray sheet detection unit 45 includes, for example, a light receiving unit 45a and a light source 45b provided on the face and backside of the stack tray 34 (see
The folding of a sheet is carried out mainly by a middle folding unit 300 including the folding roller pair 38 made up of two folding rollers that contact each other and the folding blade 37 which inserts the sheet to be nipped between the folding roller pair 38 in appropriate timing.
The middle-folding unit 300 has the folding roller pair 38 which folds a sheet bundle into two, the folding blade 37 as a pushing member which pushes the sheet bundle into the nip part of the folding roller pair 38, and a guide member 302 which holds the folding blade 37 in a manner that the folding blade 37 is movable toward the folding roller pair 38, and which regulates fluctuation in a direction intersecting the direction of movement of the pushing member before the sheet bundle is pushed into the nip part.
The folding roller pair 38 includes a folding roller 38a and a folding roller 38b. The folding roller 38a is rotatably supported on a device frame. Meanwhile, the folding roller 38b is rotatably supported on one end 304b of an arm 304 and can move in a direction orthogonal to the direction of movement of the folding blade 37. The folding roller 38b can move toward and away from the folding roller 38a.
A spring 306 is attached to the other end 304c of the arm 304. The folding roller 38b rotates via the arm 304 rotated about a fulcrum 304a by the spring 306. In this case, a first supporting hole 304d is provided which enables the folding roller 38b to move linearly instead of arcuately.
The folding blade 37 has a blade forward end 37a which strikes the sheet bundle, first and second holding members 308 and 310 which hold the blade forward end 37a between the first and second holding members, and lateral plates 312 attached at both sides of the second holding member 310.
A stud 314 is provided on a forward part of the lateral plate 312, that is, on the side of the folding roller pair 38. A shaft 316 is attached to a rear part. The folding blade 37 is held in a slidable manner on the guide member 302 via the stud 314 and the shaft 316.
The longer the length of the shaft 316 of the stud 314 is, the more stability is obtained. Therefore, in this embodiment, the position of attachment of the stud 314 is closer to the side of the folding roller pair 38 than the blade forward end 37a. The stud 314 and the shaft 316 as sliding members are not limited to the above configuration. Both these two members may be studs or shafts. Alternatively, rotatable rolling members may also be used. The position of attachment of the stud 314 to the lateral plate 312 is not limited to the above configuration, either.
A driving unit 318 to slide the folding blade 37 is provided at both ends of the shaft 316. The driving unit 318 has a cam shaft 320 and a groove part 322a, and also has a groove cam 322 rotatable about the cam shaft 320, and a driven member 324. In the groove part 322a of the groove cam 322, a rolling member 326 such as a roller follower, for example, as a contractor, is guided rotatably. The rolling member 326 is attached to the driven member 324. A driven member rotary shaft 328 is provided at one end of the driven member 324. The driven member rotary shaft 328 is attached to the device frame. The groove cam 322 is rotated by a driving motor connected to one end of the cam shaft 320.
As the groove cam 322 rotates and the rolling member 326 is guided along the groove part 322a, the driven member 324 repeats reciprocating like a pendulum about the driven member rotary shaft 328 according to the eccentricity of the groove part 322a.
The fold reinforcing unit 50 has a fold reinforcing roller pair 51 including an upper roller 51 and a lower roller 51b. The fold reinforcing roller pair 51 moves while pressurizing a fold in a direction (direction along the fold) orthogonal to the sheet carrying direction, and thus reinforces the fold.
As shown in
As shown in
A sheet detection sensor 333 is provided in the carrying path for the sheet and detects passage of the forward edge and the rear edge of the sheet passing through the carrying path. When sending out the sheet to the stack tray 34, the assist roller 332 moves in the direction of arrow B. As the sheet detection sensor 333 detects the rear end of the sheet, after a predetermined time from this point, it is determined that the sheet is completely sent out to the stack tray 34. Then, the position of the assist roller 332 is moved in the direction of arrow A about a fulcrum P. This movement causes the assist roller 332 to contact the sheet sent out to the stack tray 34.
Since the assist roller 332 is rotated in the direction of arrow C by the carrying motor 301, the sheet sent out to the stack tray 34 is moved downward. The surface of the assist roller 332 is covered with a sponge or the like. Therefore, the assist roller 332 can move the sheet downward without damaging the sheet.
In a lower part of the stack tray 34, the stack pawl 211 is provided movably in an up-down direction. The stack pawl 211 usually stands by at a standby position S1. When the sheet is to be sent out to the stack tray 34 as described above, the stack pawl 211 moves up to a sheet receiving position S2. Then, at the sheet receiving position S2, the stack pawl 211 receives the lower end of the sheet pushed down by the assist roller 332 from the top of the slope of the stack tray 34. After that, the stack pawl 211 moves down to a folding position S3. Hereinafter, the description that the sheet is placed on the stack tray may refer to the sheet arriving at the folding position.
Next, the operation of the sheet folding device 30 will be described with reference to the flowcharts shown in
In ACT A801 in
Meanwhile, in ACT A802, when the sheet is absent on the stack tray, the processing shifts to ACT A804. The assist roller 332 is moved in the direction B (see
In the next ACT A806, the sheet is supplied to the stack tray 34 under the control of the sheet detection supply unit 71. As the sheet is placed on the stack tray 34, in ACT A807, the position of the stack pawl 211 is moved to the folding position S3 under the control of the stack pawl position control unit 72.
Then, in the next ACT A808, the assist roller 332 is moved in the direction A (see
The folding blade 37 is rectangular and has a wedged cross section with a pointed distal end on the side of the folding roller pair 38, as shown in
When the folding blade 37 is in the standby state indicated by the solid lines in
In the folding mode shown in
When the sheet is detected in ACT A811 (Y in A811), the processing shifts to ACT A812 and the timer unit 75 measures time following the start of the folding.
When the sheet is not placed in ACT A811, the sheet is placed on the stack tray 34 in ACT A811a and then time measurement is started in ACT A812. It is also possible to place the sheet on the stack tray 34 first in ACT A811 and then move the sheet to the folding position S3.
In ACT A813, the folding blade 37 is moved closer to the part between the folding rollers 38a and 38b, as shown in
In the next ACT A814, the folding blade 37 is moved away from the folding rollers 38a and 38b as shown in
In ACT A815, a lapse of a predetermined time after the timer unit 75 starts measuring time in ACT A812 is detected. Then, the processing returns to ACT A811. As the tray sheet detection unit 45 detects in ACT A811 that the second sheet P2 is placed on the stack tray 34, again, the timer unit 75 starts measuring time in ACT A812. In the next ACT A813, the second sheet P2 is folded as shown in
In this case, the second sheet is folded by the folding rollers 38a and 38b from above the first sheet P1. Similarly, as long as a sheet is detected on the stack tray 34 in ACT A811, the timer unit 75 starts measuring time in ACT A812 and the folding blade 37 is moved toward the folding roller pair 38 to perform folding under the control of the folding blade control unit 74. In ACT A814, the folding blade 37 is moved away from the folding roller pair 38. In the next ACT A815, the predetermined time is confirmed.
In this manner, the folding of the first sheet P1 is finished and the second sheet P2 is folded. Sheets are similarly folded continuously.
According to this embodiment, as folding is continuously performed, the processing time for folding per sheet can be reduced and the efficiency of the processing can be improved.
In the embodiment, the example is described in which it is detected that a sheet is placed on the stack tray, based on the interruption of light using the light source and the light receiving unit provided to face each other on the backside and face of the stack tray. The optical detection of a sheet on the stack tray may also be carried out by a light source and a light receiving unit provided in a lateral direction on the stack tray. According to the invention, it is also possible to detect a sheet by a mechanical device such as a switch, as well as such optical detection.
In the embodiment, the continuous folding of sheets is carried out in a way that according to the time from the time point of starting the preceding folding, the subsequent folding is carried out. However, instead of time, for example, it is possible to adjust the position of the tray sheet detection unit provided on the stack tray and thus carry out the folding in appropriate timing.
That is, since the sheet is supplied to the folding rollers via the aperture 34a during the folding in progress, as shown in
In the embodiment, the case where the invention is applied to a multi-functional color copier is described. However, the invention can be used as a sheet folding device of a finisher used not only in a multi-functional color copier but also in other image forming apparatuses which has an image forming unit to generate an image to be printed on a sheet and which designates sheet types for print, such as an ordinary copier, printer, or facsimile.
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 Provisional U.S. Application 61/311259 filed on Mar. 5, 2010, the entire contents of which are incorporated herein by reference.
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Number | Date | Country | |
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