Patent Grant
9187284
1. Field of the Invention
The present invention relates to a sheet discharge device and an image forming apparatus including the same.
2. Description of the Related Art
Hitherto, an image forming apparatus such as a copier, a printer, a facsimile, and a multi-function printer includes a sheet discharge device configured to discharge a sheet on which an image has been formed to a discharged sheet stacking portion provided outside of the image forming apparatus.
There is known such a sheet discharge device provided with a destaticizing brush at a sheet discharge port as disclosed in Japanese Patent Application Laid-open No. Hei. 11-171388 for example. The destaticizing brush makes it possible to stack the sheet stably on the discharged sheet stacking portion by removing static electricity accumulated in the sheet during conveyance thereof before discharging the sheet to the discharged sheet stacking portion. There is also known a sheet discharge device provided with a full-load detection lever configured to detect a full-load of sheets stacked on the discharged sheet stacking portion as disclosed in Japanese Patent Application Laid-open No. 2003-238016. The full-load detection lever also functions as a guide member guiding a sheet being discharged to the discharged sheet stacking portion.
Here, if the sheet discharge device includes the destaticizing brush and the full-load detection lever for example, it is conceivable that the destaticizing brush may be damaged by being sandwiched by the full-load detection lever and the sheet in discharging the sheet. That is, if the discharge of the sheet is continued in the state in which the destaticizing brush is sandwiched by the sheet to be discharged and the full-load detection lever, there is a possibility that tips of the destaticizing brush may be curled and deformed. If the tips of the destaticizing brush are cured, there is a possibility that parts where the destaticizing brush cannot be in contact with the sheet are brought about and it becomes unable to assure stable destaticizing performance. Still further, if the tips of the destaticizing brush are curled and if the tips of the destaticizing brush are tilted by being pushed by a front end of the sheet, and if an edge of a curled tip comes in contact with a full-load detection lever prior to a sheet, a reaction force caused by own weight of the full-load detection lever acts on the destaticizing brush. If the reaction force from the full-load detection lever acts on the destaticizing brush, there is a possibility that marks made by contact with the destaticizing brush are generated at the front end of the sheet, thus dropping quality of the sheet.
According to an aspect of the invention, a sheet discharge device includes a sheet discharge portion configured to discharge a sheet, a destaticizing brush coming into contact with the sheet discharged by the sheet discharge portion and destaticizing the sheet, and a guide member turning by being pushed by the sheet discharged by the sheet discharge portion and guiding the sheet to a stacking portion on which the discharged sheet is to be stacked. The guide member includes a guide portion guiding the discharged sheet to the stacking portion and a recede portion provided at a position facing the destaticizing brush and accepting the destaticizing brush deformed by being pushed by the sheet.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
An image forming apparatus according to an embodiment of the present invention will be explained below with reference to the drawings. The image forming apparatus of the embodiment of the present invention is a copier, a printer, a facsimile, or a multi-function printer including a sheet discharge device, configured to discharge a sheet on which an image has been formed to outside of the apparatus. The image forming apparatus will be explained by exemplifying an electro-photographic laser beam printer (referred to simply as a ‘printer’ hereinafter) 100 in the following embodiment.
At first, a schematic structure of the printer 100 of the embodiment of the present invention will be explained with reference to
As shown in
The sheet feed portion 10 includes a fed sheet stacking portion 11 on which the sheet S is stacked, and a feed roller 12 configured to feed the sheet S stacked on the fed sheet stacking portion 11 one by one.
The image forming portion 20 includes four process cartridges 21Y through 21K, respectively forming images of yellow (Y), magenta (M), cyan (C), and black (K), and exposure devices 22Y through 22K exposing surfaces of photoconductive drums 23Y through 23K described later. It is noted that because the four process cartridges 21Y through 21K are constructed in the same manner with each other except that the colors of the images to be formed are different, only the construction of the process cartridge 21Y forming the yellow (Y) image will be explained and an explanation of the process cartridges 21M through 21K will be omitted here. It is noted that reference numerals TY through TK in
The process cartridge 21Y includes a photoconductive drum 23Y, a charging roller configured to charge the photoconductive drum 23Y, and a developing roller configured to develop an electrostatic latent image formed on the photoconductive drum 23Y. The image forming portion 20 further includes an intermediate transfer belt on which toner images on the photoconductive drums 23Y through 23K are primarily transferred, and primary transfer rollers 25Y through 25K primarily transferring the toner images on the intermediate transfer belt 24. The image forming portion 20 also includes a secondary transfer portion 26 configured to secondarily transfer the toner images primarily transferred to the intermediate transfer belt 24 to a sheet S and a fixing portion 27 heating and fixing the toner images secondarily transferred to the sheet S.
The sheet discharge device 30 is provided downstream in a sheet conveying direction of the fixing portion 27 and is configured to be able to discharge the sheet S on which the image has been fixed to outside of the apparatus. It is noted that a concrete structure of the sheet discharge device 30 will be described later in detail. The discharged sheet stacking portion 40 is provided at an upper part of a casing 101 of the printer 100 and is formed to be able to stack the sheet S discharged out of the sheet discharge device 30.
As shown in
Next, the image forming operation (image forming control made by the control portion 50) of the printer 100 will be explained. When image information is inputted from an external PC or the like, the exposure devises 22Y through 22K irradiate laser beams to the photoconductive drums 23Y through 23K based on the inputted image information. At this time, the photoconductive drums 23Y through 23K are charged in advance by the charging roller, and the electrostatic latent images are formed on the photoconductive drums 23Y through 23K by the laser beams irradiated thereon. After that, the electrostatic latent images are developed by the developing roller, and the yellow (Y), magenta (M), cyan (c), and black (K) toner images are formed on the photoconductive drums 23Y through 23K. The toner images of the respective colors toner images formed on the photoconductive drums 23Y through 23K are superimposed on and transferred to the intermediate transfer belt 24 by the primary transfer rollers 25Y through 25K and are conveyed to the secondary transfer portion 26 by the intermediate transfer belt 24.
In parallel with the image forming operation described above, the sheet S stacked on the fed sheet stacking portion 11 is fed one by one by the feed roller 12 to a registration roller pair 102. The registration roller pair 102 corrects a skew of the sheet S and conveys the sheet S to the secondary transfer portion 26 at a predetermined conveyance timing to transfer the toner images on the intermediate transfer belt 24 to the sheet S. The sheet S on which the toner images have been transferred is then conveyed to the fixing portion 27 to fix the toner images. The sheet S is discharged by the sheet discharge device 30 to the discharged sheet stacking portion 40 and is sequentially stacked thereon. A specific discharging operation performed when the sheet S is discharged by the sheet discharge device 30 will be described later in detail.
Next, the sheet discharge device 30 described above will be specifically explained with reference to
As shown in
The discharge lower and upper guides 31 and 32 are provided downstream in the sheet conveying direction of the fixing portion 27 and guide the sheet S on which the image has been fixed in the fixing portion 27 to the nip N of the discharge roller pair 33 by lower and upper guide surfaces 31a and 32a thereof. It is noted that the discharge lower and upper guides 31 and 32 compose the casing (apparatus body) in a case where the sheet discharge device is the sheet discharge device.
The discharge roller pair 33 includes a discharge lower roller 33a rotatably supported by the discharge lower guide 31 and a discharge upper roller 33b rotatably supported by the discharge upper guide 32, and discharges the sheet S guided by the discharge lower and upper guides and 32 to outside of the apparatus. Specifically, the discharge lower and upper rollers 33a and 33b are connected to a driving source not shown through gears 36a and 36b, and are configured to rotate by being driven by the driving source. It is noted that although the discharge lower and upper rollers 33a and 33b are configured to rotate by being driven by the driving source in the present embodiment, it is possible to adopt a configuration in which one roller is driven by the other roller driven by the driving source.
The destaticizing brush 34 is provided downstream in the sheet discharge direction of the discharge roller pair 33 and removes electricity of the sheet S discharged by the discharge roller pair 33. The destaticizing brush 34 includes a plurality of hair-bundles (brush portion) 34a disposed substantially in parallel with a width direction orthogonal to the sheet discharge direction and coming into contact with the sheet S, and a support portion (base portion) 34b supporting the plurality of hair-bundles 34a. Each of the plurality of hair-bundles 34a is conductive and is formed of elastic stainless steel which is elastically deformable by coming into contact with the sheet S. Each of the plurality of hair-bundles 34a extends downward beyond the nip N of the discharge roller pair 33 and removes electric charge of the sheet S by coming into contact with the sheet S discharged out of the discharge roller pair 33. It is noted that the hair-bundle here means what is composed of two or more hairs, it may be composed of one hair. The support portion 34b is formed of a conductive material and is supported by the discharge upper guide 32 in a vicinity of the discharge roller pair 33. The support portion 34b is formed such that a length thereof is longer than a widthwise length of the sheet S that can be discharged by the sheet discharge device 30. The support portion 34b supports the plurality of hair-bundles 34a substantially at equal intervals substantially across an entire range in the width direction.
The full-load detection portion 35 includes a plurality of detection levers (guide member) 36 turnable centering on a rotational shaft 37 disposed downstream in the sheet discharge direction of the discharge roller pair and above the discharge roller pair 33, and detection sensor 35a (see
As shown in
Each of the detection lever 36 includes an abutment portion 38a provided at a front end side of the lever and is abuttable against the upper surface of the sheet S stacked on the discharged sheet stacking portion 40, and a plurality of guide portions 39 provided on a side of the base end (side of the rotational shaft 37) and capable of guiding the discharged sheet S to the discharged sheet stacking portion 40. The detection lever 36 also includes a recede portion 38b provided on the side of the base end and formed into a concave shape to depress in a direction opposite from a direction in which the plurality of guide portions 39 project. It is noted that this recede portion 38b composes a concave portion formed by the guide portions 39 and a surface 380 (see
More specifically, as shown in
The rotational shaft 37 is turnably supported to the discharge upper guide 32 in a vicinity of the support portion 34b of the destaticizing brush 34. The plurality of detection levers 36 is linked to the rotational shaft 37 such that they are synchronized with each other. The plurality of detection levers 36 is configured such that the plurality of detection levers 36 turns centering on the rotational shaft 37 when the plurality of detection levers 36 is pushed by the sheet S.
The sheet discharging operation performed by the sheet discharge device 30 constructed as described above will be explained with reference to
The sheet S on which the toner image has been fixed by the fixing portion 27 is conveyed to the sheet discharge device 30 by the roller pair in the fixing portion 27. The sheet S conveyed to the sheet discharge device 30 is guided by the lower guide surface 31a of the discharge lower guide and the upper guide surface 32a of the discharge upper guide 32 to the nip N of the discharge roller pair 33 and is discharged out of the apparatus by the discharge roller pair 33.
At this time, static electricity accumulated in the sheet S during its conveyance is removed (destaticized) as the sheet S being conveyed by the discharge roller pair 33 come into contact with the destaticizing brush 34 as it passes through the nip N. Specifically, the front end of the sheet S comes into contact with the plurality of hair-bundles 34a at first. When the sheet S is conveyed further, the plurality of hair-bundles 34a tilt by being pushed by the front end of the sheet S, and the removal of electricity is achieved as the tilted plurality of hair-bundles 34a come into contact with the upper surface of the moving sheet S. Because the plurality of hair-bundles 34a of the destaticizing brush 34 is disposed substantially at equal intervals in a range (region) longer than a widthwise length of the sheet S, the hair-bundles 34a come into contact with the sheet uniformly and the removal of electricity of the sheet S can be achieved reliably without dropping the destaticizing performance.
The sheet S that has tilted the plurality of hair-bundles 34a abut next against the plurality of guide portions 39 provided in each of the plurality of detection levers 36 and presses the plurality of detection levers 36 through the plurality of guide portions 39. The plurality of detection levers 36 pressed by the sheet S turns clockwise centering on the rotational shaft 37 as shown in
At this time, the plurality of hair-bundles 34a is positioned (enter) the recede portions 38b of the detection lever 36 when the hair-bundle 34a tilts by being pushed by the front end of the sheet S. It is noted that because the sheet S is guided by the plurality of guide portions 39 projectively formed from the recede portion 38b, the sheet S will not enter the recede portion 38b. Therefore, the hair-bundles 34a are not sandwiched between the sheet S and the plurality of detection levers 36 even if the sheet S presses the plurality of guide portions 39 and when the plurality of detection levers 36 guides the sheet S. This makes it possible to reduce damages otherwise caused in the destaticizing brush 34 that destaticizes the sheet S. Still further, as shown in
When the sheet discharging operation performed by the discharge roller pair 33 ends after that, the plurality of detection levers 36 turns counterclockwise by their own weight and biases and presses the sheet S to the discharged sheet stacking portion 40 by their own weight. When the detection lever 36 reaches a predetermined rotational position after repeating these operations, the detection sensor 35a sends the predetermined detection signal. Then, the control portion 50 stops the image forming operation by receiving the predetermined detection signal. Then, if a job is left, the image forming operation is restarted if a user or the like removes the sheet bundle stacked on the discharged sheet stacking portion 40. The control portion ends the image forming process as it is if the job has been finished.
As described above, according to the printer 100 of the present embodiment, the hair-bundles 34a will not be sandwiched between the sheet S and the plurality of detection levers 36 even when the sheet is guided by the plurality of detection levers 36. Therefore, it is possible to prevent the hair-bundles 34a from being put into a state in which the hair-bundles 34a are rubbed and drawn and to prevent the tips of the hair-bundles 34a from being deformed in a curled manner. This arrangement makes it possible to prevent the destaticizing performance from being lowered due to a decrease of an area of contact with the sheet S caused by the curled hair-bundles. As a result, it becomes possible to adequately remove the static electricity charged to the sheet and to stably stack the sheet on the discharged sheet stacking portion 40.
Still further, it is possible to prevent the quality of the sheet S from dropping by contact marks and the like that can be generated when the curled hair-bundles 34a come in contact with the sheet S by preventing the deformation such as curling.
Still further, because the provision of the recede portion 38b permits the detection lever 36 to be disposed in the vicinity of the destaticizing brush 34, the sheet discharge device can be downsized. That is, the printer can be downsized. Still further, because it becomes possible to detect an upstream end in the sheet discharge direction of the sheet S stacked on the discharged sheet stacking portion 40 by disposing the detection lever 36 in the vicinity of the destaticizing brush 34, it is possible to improve accuracy of the full-load detection.
Still further, because it is not necessary to dispose the destaticizing brush while avoiding the detection levers, the hair-bundles can be disposed at equal intervals (uniformly) in the entire sheet widthwise region. Due to that, it is possible to prevent the destaticizing performance of the destaticizing brush 34 from dropping.
While the embodiment of the present invention has been explained above, the present invention is not limited to the embodiment described above. The advantageous effects described in the embodiment of the present invention are also mere enumeration of the most preferable effects brought about from the present invention, so that the effects of the present invention are not limited to those described in the embodiment of the invention.
Still further, while the detection lever 36 is constructed to be turnable centering on the rotational shaft 37 in the present embodiment, it is not always necessary to construct the detection lever to be turnable if a sheet guide function is to be simply given to the detection lever. In this case, the detection levers 36 may be constructed as a comb-like member composed of only the guide portions 39 and the recede portions 38b between the guide portions 39. Still further, the guide portion 39 may be configured to be turnable and to extend downward so that the lower part of the guide portion 39 is able to come in contact with the upper surface of the sheet on the discharged sheet stacking portion 40. This configuration makes it possible to detect a sheet stacking amount on the discharged sheet stacking portion 40 by the guide portion 39 being turned by in contact with the upper surface of the sheet on the discharged sheet stacking portion 40. Still further, it is not always necessary to integrate the guide portion 39 with the detection lever 36, and it is possible to configure such that the detection lever 36 is turned through the guide portion 39 separately constructed. While the present embodiment has been explained by exemplifying the electro-photographic printer, the present invention is not limited to that. For instance, the present invention is also applicable to an ink-jet type printer (image forming apparatus) forming an image on a sheet by discharging ink droplets from a nozzle.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2013-172141, filed on Aug. 22, 2013, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-172141 | Aug 2013 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4951935 | Oikawa | Aug 1990 | A |
| 4994861 | Brandon et al. | Feb 1991 | A |
| 5713060 | Sato et al. | Jan 1998 | A |
| 6487379 | Sato | Nov 2002 | B2 |
| 7883079 | Sato et al. | Feb 2011 | B2 |
| 20090189344 | Suzuki | Jul 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 11-171388 | Jun 1999 | JP |
| 2003-238016 | Aug 2003 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20150054215 A1 | Feb 2015 | US |
