Patent Application
20120074638
The present application claims priority from Japanese patent application number 2010-217976, filed on Sep. 28, 2010, the entire contents of which are incorporated by reference herein.
The present invention relates to a sheet conveyance device and an image forming apparatus including the sheet conveyance device, and in particular relates to a sheet conveyance device including a conveyance belt to convey a sheet while contacting a driving roller to be driven in a predetermined direction and a guide plate to guide the sheet disposed downstream of the conveyance belt driving direction and spaced away from the belt.
Generally, in image forming apparatuses, a recording sheet such as a sheet of paper is conveyed from one predetermined place to another by a sheet conveyance device. Such a sheet conveyance device includes an internal conveyance path defined by a plurality of guide plates and a plurality of rollers or a belt which are rotatably driven to convey the sheet.
An image forming apparatus 100 includes a sheet conveyance section 180 which includes a sheet feed bank 110, a registration unit 120, and a duplex-sheet discharge unit 130. The duplex sheet-discharge unit 130 includes a fixing unit 140 and a sheet conveyance device 150.
The image forming apparatus 100 includes an intermediate transfer device 160 which includes image carriers of yellow, magenta, cyan, and black 170Y, 170M, 170C, and 170Bk, respectively, and an intermediate transfer belt 161.
A toner image formed by the image carriers 170Y, 170M, 170C, and 170Bk is transferred to the intermediate transfer belt 161. A sheet S fed from the sheet feed bank 110 is conveyed to the intermediate transfer device 160, and the toner image on the intermediate transfer belt 161 is transferred onto the sheet S. The toner image on the sheet S is fixed by the fixing unit 140 and the sheet S is discharged by the sheet conveyance device 150.
The sheet conveyance device 150 includes a driving roller 210, a driven roller 220, and a conveyance belt 230 stretched over the driving roller 210 and the driven roller 220. The conveyance belt 230 is a wide single conveyance belt. The conveyance belt 230 includes a cooling roller 240 to contact and cool the sheet S being conveyed, and contact rollers 250, 260 positioned opposite the driving roller 210 and the driven roller 220, respectively. As illustrated in
In such a sheet conveyance device 150, the driven roller 220 and the conveyance belt 230 stretched over the surface of the driven roller 220 are rotatably driven, so that the driven roller 220 and a lower guide plate 292 are not in contact with each other, that is, a slight gap D is present between the driven roller 220 and the lower guide plate 292. Therefore, when the leading edge of the sheet S has a downward curl, the sheet S may be introduced into the gap D between the driven roller 220 and the lower guide plate 292. In this case, the sheet S does not reach a downstream sheet sensor 460, and therefore, the sheet sensor 460 determines that a paper jam has occurred.
In such a case, if the trailing edge of the sheet S stops before the gap D, the upper guide plate 291 is moved out of the way to allow the sheet S to be pulled out by the leading edge thereof, thereby removing the sheet S. By contrast, if the trailing edge of the sheet S passes completely through the gap D, the sheet S has been already introduced into the depths of the device (indicated by arrow S2 in the figure) and it is not easy to remove the sheet S. To remove the sheet S, disassembly of the device, such as removal of the guide plate and/or the conveyance roller, is needed, which is troublesome.
In addition, even if the trailing edge of the sheet stops before the gap D, erroneous turning of a knob 221 illustrated in
To prevent such a sheet jam, JP-2010-024029-A discloses a configuration in which a stopper member stretched over the driven roller and the guide member is provided between the driven roller and the guide plate disposed downstream of the sheet conveyance direction to prevent the conveyed sheet from entering into a gap between the driven roller and the guide plate. In this arrangement, however, the conveyance belt needs to be divided into plural parts laterally, in order to accommodate the stopper, which is physically impossible to do if the conveyance belt is wide one.
In addition, if the conveyance belt is divided into plural parts, the sheet conveyed by the conveyance belt and the cooling roller inevitably loses the desired uniform contact with the belt in some parts. In this case, a pressure difference arises between one part closely contacting the sheet and another contacting the sheet loosely or not at all, which may cause uneven glossiness in the final printed image.
As described above, because the conventional sheet conveyance device includes a gap between the conveyance roller and the guide plate, if a paper jam occurs, the sheet enters the gap. In such a case, it is not easy to remove the jammed paper and disassembly of the guide plate and the conveyance roller is required to remove the sheet, which may take a lot of time and trouble.
The present invention aims to solve the aforementioned problems, and provides an improved sheet conveyance device for use in the image forming apparatus, allowing easy removal of a jammed sheet stuck in a gap between a conveyance roller and the guide plate.
As an aspect of the present invention, a sheet conveyance device according to the present invention includes an upstream rotary member and a downstream rotary member; an endless rotatable conveyance belt, stretched over the upstream rotary member and the downstream rotary member, to convey a sheet of recording media thereon in a predetermined conveyance direction; a conveyance guide disposed downstream of the conveyance belt in the predetermined conveyance direction, disposed across a gape from the conveyance belt, to guide the sheet to a predetermined conveyance position; and a planar guide member to introduce the sheet into the gap between the conveyance belt and the conveyance guide and onto the conveyance belt, so that the sheet is conveyed from the downstream rotary member to the upstream rotary member.
These and other objects, features, and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.
Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.
As illustrated in
In the present embodiment, the upstream guide plate 270 includes an upper guide plate 271 and a lower guide plate 272. The upper guide plate 271 is configured to be openable in an arrow B direction as illustrated in
The conveyance belt 230 includes a cooling roller 240 to contact and cool down the sheet P which is being conveyed, and rollers 250 and 260 to contact the conveyance belt 230 disposed opposite the driving roller 210 and the driven roller 220, respectively. In this case, a slight gap D is present between the driven roller 220 and the lower guide plate 292. A guide plate 500 is disposed at a lower side of the conveyance belt 230 which forms a conveyance path to guide the sheet S entering from the gap D to an inlet of the sheet conveyance device 150.
Next, operation of the sheet conveyance device 150 according to an embodiment of the present invention will now be described. As illustrated in
If the leading edge of the sheet S is curled downward, the sheet S tends to enter the gap D between the driven roller 220 and the lower guide plate 292. Specifically, the sheet S is accompanied by a rotation of the driven roller 20, is deviated from the normal conveyance path S1, and enters inside the apparatus S2. Then, when the sheet sensor 460 does not detect a leading edge of the sheet S, it is determined that a sheet jam occurs, and conveyance of the sheet S is stopped. At this time, the sheet S stops between the conveyance belt 230 and the guide plate 500.
As illustrated in
As described above, the sheet conveyance device 150 according to an embodiment of the present invention is capable of enabling the jammed sheet to be removed easily at the inlet S3 of the sheet conveyance device 150 even when the sheet S enters the gap between the driven roller 220 and the lower guide plate 292.
Further, as can be appreciated by those skilled in the art, the guide plate 500 according to the present embodiment can be adapted to the sheet conveyance device of a conventional image forming apparatus. By installing the present guide plate 500 in a currently available sheet conveyance device, the problem of paper jams may be easily solved.
Further, as illustrated in
Additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-217976 | Sep 2010 | JP | national |
