Toner conveying device

A toner conveying device includes a common conveyance path, toner input paths and blades. A screw for conveying a toner is installed in the common conveyance path. The toner input paths extend in an up-down direction and have lower ends connected to the common conveyance path. The blades are installed so as to make contact with a shaft of the screw and are configured to scrape off a toner adhering to the shaft of the screw. The blades are arranged immediately below the toner input paths so as to make contact with the shaft of the screw. The blades are disposed at a pitch of an integer multiple of a pitch of the fin of the screw.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-231612 filed on Nov. 7, 2013, the entire contents of which are incorporated herein by reference.

BACKGROUND

The technology according to one aspect of the present disclosure relates to a toner conveying device.

An image forming apparatus such as, e.g., a laser printer or a multifunction peripheral, includes a toner conveying device that conveys a residual toner removed from an outer circumferential surface of the a photosensitive drum by a cleaning device.

The toner conveying device includes a common conveyance path for conveying a toner to a toner collection container, and a plurality of toner input paths connected to the common conveyance path.

The common conveyance path extends in the horizontal direction. A screw for conveying a toner is installed within the common conveyance path. The screw includes a screw shaft extending along the common conveyance path and a spiral fin one-piece formed with the screw shaft such that the spiral fin is wound around the screw shaft. The toner input paths extend in the up-down direction. The lower ends of the toner input paths are connected to the common conveyance path. The toner conveying device is configured to drop the toner from the toner input paths into the common conveyance path and to convey the toner with the rotating screw.

SUMMARY

A toner conveying device according to one aspect of the present disclosure includes a common conveyance path, toner input paths and blades. A screw for conveying a toner is installed in the common conveyance path. The toner input paths extend in an up-down direction and have lower ends connected to the common conveyance path. The blades are installed so as to make contact with a shaft of the screw and are configured to scrape off a toner adhering to the shaft of the screw. The blades are arranged immediately below the toner input paths so as to make contact with the shaft of the screw. The blades are disposed at a pitch of an integer multiple of a pitch of the fin of the screw.

DETAILED DESCRIPTION

An embodiment of the present disclosure will now be described in detail with reference to the accompanying drawings. The technology of the present disclosure is not limited to the following embodiment.

FIG. 1is a sectional view showing a schematic structure of an image forming apparatus1. The image forming apparatus1is, e.g., a tandem-type color printer. As shown inFIG. 1, the image forming apparatus1includes an intermediate transfer belt7, primary transfer units8, a secondary transfer unit9, a fixing unit11, an optical scanner15, and a plurality of image forming units16.

A sheet feeding cassette3is disposed at the inner lower side of a body2of the image forming apparatus1. The sheet feeding cassette3accommodates therein unprinted sheets (not shown) such as cut papers or the like in a stacked state. A first sheet conveying unit21is installed at one lateral side of the sheet feeding cassette3. The first sheet conveying unit21receives a sheet sent from the sheet feeding cassette3and conveys the sheet toward the secondary transfer unit9positioned at the upper side thereof.

A manual sheet feeding unit5is installed at the right side of the sheet feeding cassette3. A second sheet conveying unit22is installed at the left side of the manual sheet feeding unit5. The second sheet conveying unit22receives a sheet sent from the manual sheet feeding unit5and conveys the sheet toward the first sheet conveying unit21.

The optical scanner15is disposed at the upper side of the second sheet conveying unit22. Based on the image data received by the image forming apparatus1, the optical scanner15irradiates laser light toward the image forming units16. The image forming units16are installed above the optical scanner15. An endless intermediate transfer belt7is installed above the respective image forming units16. The intermediate transfer belt7is wound around a plurality of rollers and is rotationally driven by a drive device not shown.

As shown inFIG. 1, four image forming units16are disposed in one row along the intermediate transfer belt7. Each of the image forming units16forms an image of yellow (Y), magenta (M), cyan (C) or black (K).

Each of the image forming units16includes a photosensitive drum31as a photosensitive body, a charger32, a developing device33and a cleaning device10, the latter three of which are disposed around the photosensitive drum31.

The photosensitive drum31is rotationally driven by a drive motor not shown. The charger32uniformly charges the outer circumferential surface of the photosensitive drum31at a predetermined electric potential using a charging bias voltage applied by a charging bias power supply not shown. Each of the photosensitive drums31is configured such that an electrostatic latent image can be formed on the photosensitive drum31by writing the light emitted from the optical scanner15onto the photosensitive drum31.

Each of the developing devices33accommodates a magenta toner, a cyan toner, a yellow toner or a black toner and develops an electrostatic latent image by affixing the toner to the electrostatic latent image of each of the photosensitive drums31on a color-by-color basis, thereby visualizing the electrostatic latent image of each of the photosensitive drums31as a toner image.

The primary transfer units8are respectively disposed above the respective image forming units16. The primary transfer units8include transfer rollers that primarily transfer the toner images formed by the image forming units16to the surface of the intermediate transfer belt7.

In the meantime, a residual toner or a foreign material such as a byproduct or the like adhere to the outer circumferential surface of the photosensitive drum31from which the toner images have been transferred to the intermediate transfer belt7. The cleaning devices10of the image forming units16clean the outer circumferential surface of the photosensitive drum31, thereby removing the residual toner and the foreign material.

The intermediate transfer belt7is rotationally driven and the toner images of the respective image forming units16are transferred to the intermediate transfer belt7, whereby a color image composed of the toner images of four colors, i.e., yellow, magenta, cyan and black, which overlap with one another, is formed on the surface of the intermediate transfer belt7.

As shown inFIG. 1, the secondary transfer unit9includes a transfer roller18disposed at the left side of the intermediate transfer belt7. The toner image of the intermediate transfer belt7is transferred to the sheet by the transfer roller18.

The fixing unit11is disposed above the secondary transfer unit9. A third sheet conveying unit23for conveying the sheet, to which the toner image has been transferred, toward the fixing unit11is disposed between the secondary transfer unit9and the fixing unit11.

The fixing unit11includes a fixing roller19and a pressing roller20which are rotated independently of each other. The sheet is heated and pressed by the fixing roller19and the pressing roller20, whereby the toner image is fixed to the sheet.

As described above, in the image forming apparatus1, the optical scanner15optically scans the photosensitive drums31based on the image data. Thus, the electrostatic latent images are formed on the photosensitive drums31. Thereafter, the electrostatic latent images of the photosensitive drums31are developed as the toner images of the respective colors by the developing devices33. Subsequently, the toner images of the respective colors are transferred from the photosensitive drums31to the intermediate transfer belt7by the primary transfer units8. In the secondary transfer unit9, the toner image of the intermediate transfer belt7is transferred to the sheet conveyed from the first sheet conveying unit21. Thereafter, the sheet to which the toner image is fixed by the fixing unit11is discharged toward a sheet discharge part28.

The image forming apparatus1further includes a toner conveying device35that conveys the residual toner removed from the outer circumferential surfaces of the photosensitive drums31by the cleaning devices10.FIG. 2shows the outward appearance of the toner conveying device35.FIG. 3shows the cross-sectional structure of the toner conveying device35connected to a connection pipe36.

As shown inFIGS. 2 and 3, the toner conveying device35includes a toner conveyance pipe37extending in the horizontal direction and a plurality of toner input units38connected to the conveyance pipe37. The toner input units38are disposed at a predetermined pitch P1 along the longitudinal direction of the conveyance pipe37.

The inside of the conveyance pipe37constitutes a common conveyance path42for conveying a toner to a toner collection container (not shown). A screw45for conveying a toner is installed in the common conveyance path42. A shutter unit46for opening and closing the common conveyance path42is installed at one end of the common conveyance path42. As the shutter unit46is opened, the common conveyance path42communicates with the toner collection container.

FIG. 4is an enlarged side view showing a portion of the screw45. As shown inFIGS. 3 and 4, the screw45includes a screw shaft47extending along the common conveyance path42and a spiral fin48one-piece formed with the screw shaft47such that the spiral fin48is wound around the screw shaft47. The screw45is rotationally driven by a drive mechanism (not shown) such as a drive motor or the like and is configured to convey a toner toward the shutter unit46(in a conveyance direction A inFIG. 2).

The screw45is manufactured by injection molding. The screw45has such a shape that, when molds divided into two parts are removed during the manufacture of the screw45, an undercut is not generated in the fin48. That is to say, as shown inFIG. 4, the fin48includes increased width portions49having a relatively large width in the axial direction of the screw45. The increased width portions49are disposed at a predetermined pitch in the axial direction of the screw45.

As shown inFIGS. 2 and 3, the toner input units38include toner input paths43extending in the up-down direction and having lower ends connected to the common conveyance path42, and connection ports44kept in communication with the toner input paths43and opened toward a lateral side.

The distal ends of connection pipes46are connected to the connection ports44. The base ends of the connection pipes36are connected to the cleaning devices10. The toner is supplied from the cleaning devices10to the base ends of the connection pipes36. That is to say, the toner input paths43are connected to the cleaning devices10through the connection pipes36. A screw not shown is installed within each of the connection pipes36. By the rotation of the screw, the toner supplied from the cleaning devices10is conveyed toward the connection ports44of the toner input units38. The toner conveyed to the toner input units38freely falls along the toner input paths43and enters the common conveyance path42. The toner existing in the common conveyance path42is conveyed toward the shutter unit46by the screw45as set forth above.

The toner conveying device35includes blades51for scraping off the toner adhering to the screw45. The blades51are formed of elastic sheets such as, e.g., PET films or the like. The base end portion of the each of the blades51is attached and fixed to the inner wall surface of each of the toner input units38, whereby the blades51are fixed in the toner input paths43. Alternatively, the blades51may be fixed to the inner wall surface of the common conveyance path42. As shown inFIG. 4, the distal end portion of each of the blades51extends downward and makes contact with the screw shaft47. This makes it possible to efficiently scrape off the toner adhering to the screw shaft47.

FIG. 5is a side view schematically showing the relationship between the screw45and the blades51. As shown inFIGS. 2 and 5, the blades51are disposed at the same pitch as the pitch P1 of the toner input units38(namely, the pitch of the toner input paths43). The blades51are respectively disposed immediately below the toner input paths43. The blades51are disposed at a pitch of an integer multiple of the pitch P2 of the fin48. For example, in the example shown inFIG. 5, the pitch P1 of the blades51is four times as large as the pitch P2 of the fin48.

In a hypothetical case where the blades51are not installed, the toner is easy to adhere to the screw shaft47in the regions where the toner is inputted (namely, the regions existing immediately below the toner input paths43). In contrast, in the present embodiment, the blades51are disposed so as to make contact with the screw shaft47in the regions existing immediately below the toner input paths43. This makes it possible to efficiently scrape off the toner which tends to adhere to the screw shaft47.

In the meantime, as shown inFIG. 4, the increased width portions49are formed in the fin48of the screw45at a predetermined pitch in order to prevent generation of an undercut during a molding process. Therefore, the gap between the adjoining roots of the fin48becomes narrow near the increased width portions49. For that reason, in the screw45mentioned above, it is difficult to reliably bring all the blades51into contact with the screw shaft47.

In contrast, in the present embodiment, the blades51are disposed at the pitch P1 of an integer multiple of the pitch P2 of the fin48. It is therefore possible to reliably bring all the blades51into contact with the screw shaft47.

That is to say, according to the present embodiment, all the blades51can be reliably brought into contact with the screw shaft47in the regions existing immediately below the toner input paths43where the toner is easy to adhere to the screw shaft47. It is therefore possible to appropriately suppress adherence of the toner to the screw shaft47. As a result, the toner conveyance ability of the toner conveying device35can be kept high. In a high temperature environment or a high humidity environment, the adherence of the toner to the screw shaft47becomes a great problem. According to the toner conveying device35described above, it is possible to appropriately maintain the toner conveyance ability even in the high temperature environment or the high humidity environment.

In the aforementioned embodiment, the color printer has been described as one example of the image forming apparatus. However, the image forming apparatus is not limited to the color printer. The image forming apparatus may be, e.g., a copier, a scanner, a multifunction peripheral or other image forming apparatuses.

As described above, the technology of the present disclosure is useful in the toner conveying device and the image forming apparatus provided with the toner conveying device.