1. Field of the Invention
The present invention relates to a sheet conveying device for conveying a sheet to an image forming section, and an image forming apparatus provided with the same, such as a digital copying machine, laser printer and the like. Particularly, it relates to a sheet jam processing function at the time of sheet conveyance.
2. Description of the Related Art
A conventional image forming apparatus is provided with an image forming section at a center thereof. In the image forming section, a predetermined image is formed by respective steps of charging, exposing, developing, and transferring. In order to form a fine image by using the image forming section, it is necessary to control the timing at which a sheet is conveyed to the image forming section and to correct an oblique conveyance of the sheet. For this reason, the conventional image forming apparatus is provided with a sheet conveying device including a registration roller and peripheral members thereof as disclosed in Japanese Unexamined Patent Publication No. Hei. 5-58500.
In a state that the registration rollers 14 are suspended, a leading end of the sheet conveyed through the pair of conveying rollers 13 and the sheet conveyance passage 22 comes into contact with a nip portion of the pair of registration rollers 14 and the oblique conveyance of the sheet is corrected. Thereafter, the pair of registration rollers 14 are driven to convey the sheet in synchronization with the timing of the image formation of the image forming section. A registration guide 23 is provided above the sheet conveyance passage 22 between the pair of registration rollers 14 and the pair of conveying rollers 13.
A detecting sensor 24 detects a presence of the sheet which passes through the sheet conveyance passage 22, and is provided in the vicinity of the registration guide 23 in such a manner that an emitting surface of the detecting sensor faces the sheet conveyance passage 22. The detecting sensor 24 detects a passing of the leading end of the sheet, and the detection is sent to a controlling section (not shown) of a main body of the image forming apparatus. A contact-making amount (slackness amount) of a sheet against the pair of registration rollers 14 is determined by controlling the time period from the passing of the leading end of the sheet to a stopping of the driving of the pair of conveying rollers 13 by the controlling section. Further, the detecting sensor 24 detects a non-standardized sheet by continuously detecting the sheet from the leading end to the tailing end to detect a size of the sheet. The sheet size is used when the controlling section determines a suspension time of the pair of registration rollers 14 and a suspension time of the image formation.
In the foregoing conventional image forming apparatus, the registration guide 23 (see
However, a user is required to stretch his/her arm into a narrow space in the vicinity of the pair of the registration rollers 14 to rotate the registration guide 23 to remove the jammed sheet. In addition to that, the space for the pivotal of the registration guide 23 is limited due to the drum unit 20 positioned above the pair of registration rollers 14. Accordingly, it has not been easy to conduct the sheet jam processing. Further, there is not any means for rotating the registration guide 23. Consequently, the operation is troublesome.
It is an object of the present invention to provide a sheet conveying device which can ensure an easy sheet jam processing in the vicinity of a registration roller, and an image forming apparatus provided with the same.
According to an aspect of the present invention, a sheet conveying device includes a registration roller for correcting an oblique conveyance of a sheet by making contact with the sheet, and conveying the sheet in accordance with the timing of an image formation; a conveying roller mounted on an upstream of the registration roller in a sheet conveyance direction for conveying the sheet from a sheet supplying device to the registration roller; and a guide member provided between the registration roller and the conveying roller. The guide member is pivotably supported, and its pivotal axis is in an upstream of a sheet conveyance passage between the registration roller and the conveying roller. The guide member is selectively shiftable over a first position of defining a part of the sheet conveyance passage and a second position of opening an upper portion of the sheet conveyance passage.
According to another aspect of the present invention, an image forming apparatus includes such a sheet conveying device and a unit detachably mounted above the guide member of the sheet conveying device.
With the above arrangement, the guide member is pivotably supported, and its pivotal axis is on the upstream of the sheet conveyance passage between the registration roller and the conveying roller, and the guide member is selectively shiftable over the first position and the second position. Accordingly, in comparison with the conventional configuration having the pivotal axis on a downstream of the sheet conveyance passage, the space for the pivotal of the guide member is so large that the pivotal operation of the guide member can be easily conducted. As a result, the jammed sheet can be easily removed since the sheet conveyance passage is widely exposed.
Hereinafter, an embodiment of the present invention is described referring to the drawings.
An image forming apparatus 100 shown in
Next, the image forming section P is described in detail. A charger 3, an exposing unit 4, a developing unit 5, and a cleaning portion 9 are provided around and above the photoconductive drum 2 which is rotatably mounted. The charger 3 is adopted for charging the photoconductive drum 2. The exposing unit 4 is adopted for exposing image information on the photoconductive drum 2. The developing unit 5 is adopted for forming the toner image on the photoconductive drum 2. The cleaning portion 9 is adopted for removing developing agent particles (toner particles) remaining on the photoconductive drum 2.
First, the charger 3 charges a peripheral surface of the photoconductive drum 2 uniformly, then the exposing unit 4 emits a light beam to form a electrostatic latent image in accordance with an image signal on the photoconductive drum 2. A toner container 10 is installed in the developing unit 5. Toner particles in the toner container 10 is supplied to the photoconductive drum 2 by the developing unit 5 and electrostatically attached thereon so that a toner image is formed in accordance with the electrostatic latent image formed by the exposure from the exposing unit 4.
Sheets 6 are accommodated in a sheet supplying cassette 11a or stacked in a stack bypass 11b (a manually supplying tray) provided in a side of an upper pair of sheet supplying rollers 12. A sheet 6 to which a toner image is to be transferred is supplied from the sheet supplying cassette 11a and the like through the pair of sheet supplying rollers 12, a pair of conveying rollers 13, and a pair of registration rollers 14, to the image forming section P, and conveyed to a position where the photoconductive drum 2 is arranged.
At this time, in the state that the pair of registration rollers 14 are suspended, a leading end of the sheet conveyed through the pair of conveying rollers 13 and the sheet conveyance passage 22 comes into contact with a nip portion of the pair of registration rollers 14 and an oblique conveyance of the sheet is corrected. Thereafter, the pair of registration rollers 14 are driven to convey the sheet in synchronization with the timing of the image formation of the image forming section P. A registration guide 23 is an example of a guide member, and provided between the pair of registration rollers 14 and the pair of conveying rollers 13. A bottom surface of the registration guide 23 defines an upper surface of the sheet conveyance passage 22 between the pair of registration rollers 14 and the pair of conveying rollers 13.
Further, a detecting sensor (not shown) detects a presence of the sheet which passes through the sheet conveyance passage 22, and is provided in the vicinity of the registration guide 23 in such a manner that an emitting surface of the detecting sensor faces the sheet conveyance passage 22. The detecting sensor detects a passing of the leading end of the sheet, and the detection is sent to a controlling section (not shown) of the main body of the image forming apparatus. A contact-making amount (slackness amount) of a sheet against the pair of registration rollers 14 is determined by controlling the time period from the passing of the leading end of the sheet to a stopping of the driving of the pair of conveying rollers 13 by the controlling section. Further, a detecting sensor 24 continuously detects a non-standardized sheet from the leading end to the tailing end to detect a size of the sheet. The sheet size is used when the controlling section determines a suspension time of the pair of registration rollers 14 and a suspension time of the image formation.
As mentioned above, an image formation signal is turned ON in synchronization with the timing when the conveyance of a sheet 6 from the pair of registration rollers 14 is permitted, and an image is formed on the photoconductive drum 2. Underneath the photoconductive drum 2, the toner image formed on the photoconductive drum 2 is transferred onto the sheet 6 owing to an electric field generated by the transferring roller 16 applied with a predetermined transferring voltage.
The sheet 6 onto which the toner image has been transferred leaves from the photoconductive drum 2, and is conveyed to the fixing section 7. The photoconductive drum 2 from which the toner image has been transferred, toner particles remaining on the peripheral surface of the photoconductive drum are removed by the cleaning portion 9 for subsequent formation of a new electrostatic latent image. The sheet 6 conveyed from the image forming section P to the fixing section 7 is heated and pressed by a pair of fixing rollers 7a so that the toner image is fixed on the surface of the sheet 6, and the expected image is consequently formed. Thereafter, the sheet 6 bearing the image is discharged to a discharge tray 18 by a pair of discharging rollers 17.
Further, in the image forming apparatus 100 configured as mentioned above, as shown in
The registration guide 23 is supported in a downstream end portion of the multi-function frame 31 and pivotable in directions of P1 and P2 (see
An underside surface of the conveyance passage defining member 36 constitutes a part of the upper surface of the sheet conveyance passage 22 between the pair of registration rollers 14 and the pair of conveying rollers 13. The conveyance passage member 36 is formed with the engaging portions 32a, 32b at two positions on the upstream in the conveying direction. The engaging portions 32a and 32b are rotatably engaged on engagement projections 33a and 33b formed on the multi-function frame 31 (see
The registration guide 23 is provided with a plurality of ribs 35 in the direction parallel to the sheet conveying direction to ensure smooth sheet conveyance on the inner surface of the registration guide 23 or the underside surface of the conveyance passage defining member 36 that constitutes the part of the upper surface of the sheet conveyance passage 22, similarly to the conveyance frame 30. In this embodiment, the tab portion 34 is provided at the single location in the vicinity of the engaging portion 32a. However, it may be appreciated to provide a tab portion 34 in the vicinity of the engaging portion 32b, or at a center of the registration guide 23, or at two locations of left and right sides of the registration guide 23. Further, the tab portion 34 may be formed into an appropriate shape to ensure an easier operability to a user.
Next, a method of conducting a sheet jam processing by rotating the registration guide 23 is described in detail referring to
Here, supposing that a sheet 6 is jammed between the pair of conveying rollers 13 and the pair of registration rollers 14, the developing unit 5 (see
Next, in the state shown in
With this arrangement, in comparison with the conventional configuration where the pivotal axis is in the vicinity of the pair of registration rollers 14, the jammed sheet 6 can be more easily removed since the drum section 20 does not hinder the removing operation, and the pivotal space of the registration guide 23 is so large that the sheet conveyance passage 22 exposes more widely. Further, the tab portion 34 is provided on the registration guide 23 to thereby enable the registration guide 23 to be shifted to the second position only by pushing the tab portion 34. Accordingly, the provision of the above-described sheet conveying device makes it possible to provide an image forming apparatus which is easily operable, and simple, and can be produced at low costs.
Further, in
Further, the present invention is not limited to the foregoing embodiment. Various modifications may be made without departing from the scope of the present invention. For example, in the foregoing embodiment, the registration roller 23 is supported by the multi-function frame 31 on which the optional devices are mounted. However, in the case of an image forming apparatus not including the multi-function frame 31, the registration guide 23 may be attached to the other member such as a conveying frame that is provided on an upstream of the registration guide in the conveying direction.
Further, in the foregoing embodiment, the detachable developing unit 5 is mounted above the registration guide 23, and the sheet jam processing is conducted after taking the developing unit 5 off. However, it may be appreciated to adopt a configuration that allows other units than the developing unit 5 to be detachably mounted above the registration guide 23. Further, the foregoing embodiment shows, as a preferable example, the sheet conveying device which can realize the smooth sheet jam processing owing to the pivotable registration guide 23. Accordingly, it should be noted that the tab portion 34, the ribs 35 and the like are not necessarily needed.
The sheet conveying device of the present invention may be applied to various types of copying machines, such as a digital copying machine, a tandem-type color copying machine, an analogue-type monochrome copying machine, and the like, or to image forming apparatuses, such as a facsimile machine, a laser printer, and the like.
As described above, the sheet conveying device according to an embodiment of the present invention includes a registration roller for correcting an oblique conveyance of a sheet by making contact with the sheet, and conveying the sheet in accordance with the timing of the image formation; a conveying roller mounted on an upstream of the registration roller in the sheet conveyance direction for conveying the sheet from the sheet supplying device to the registration roller; and a guide member provided between the registration roller and the conveying roller. The guide member is pivotably supported, and its pivotal axis is in the upstream of the sheet conveyance passage between the registration roller and the conveying roller. The guide member is selectively shiftable over the first position of defining a part of the sheet conveyance passage and the second position of opening the upper portion of the sheet conveyance passage.
In the sheet conveying device, the guide member has the pivotal axis in the upstream of the sheet conveyance passage between the registration roller and the conveying roller, and is selectively shiftable over the first position and the second position. Thus, the turning operation of the guide member can easily be conducted in comparison with the conventional configuration which has the pivotal axis in the downstream of the sheet conveyance passage. Further, a range within which the guide member is rotatable is enlarged so that a large part of the sheet conveyance passage is exposed, to thereby provide the sheet conveying device wherein the jammed sheet can be removed easily with a simple configuration and low cost.
It may be preferable that the tab portion is provided on the conveyance upstream end portion of the guide member, and the tab portion is operable to be pressed to thereby change the guide member from the first position to the second position.
In this case, the tab portion is provided on the conveyance upstream end portion of the guide member, and the guide member is turned from the first position to the second position by pressing the tab portion. Thus, the turning operation of the guide member becomes much easier with the simple configuration.
It may be preferable that the guide member is returnable to the first position from the second position owing to release of the pressing force to the tab portion.
In this case, the guide member returns from the second position to the first position only by releasing the pressing force to the tab portion so that the guide member can be returned to the first position without fail after the completion of the sheet jam processing. Further, the guide member automatically returns to the first position only by releasing the pressing force to the tab portion, to thereby avoid a fear of the deformation or breakage of the guide member or the section due to the erroneous mounting of the section above the guide member while the guide member is in the second position, when the sheet conveying device is mounted in the image forming apparatus.
It may be preferable that the guide member further includes the conveyance passage member which defines the sheet conveyance passage, and the tab portion is integrally formed with the conveyance passage member in the direction substantially orthogonal to the main surface of the conveyance passage member.
In this case, the tab portion is formed in the direction substantially orthogonal to the main surface of the conveyance passage member so that a user can visually recognize the tab portion of the guide member easily. Thus, the sheet jam processing using the tab portion is made to be much easier, and the production cost of the guide member can be reduced since the tab portion is integrally formed with the conveyance passage member.
It may be preferable that the conveyance passage member is pivotably supported by the frame member on which the predetermined section is mountable, and the tab portion is operable to come into contact with the frame member when the guide member reaches the second position.
In this case, when the guide member reaches the second position, the tab portion comes into contact with the frame member. Thus, the user can easily operate the guide member without considering how much the guide member should be turned. Accordingly, the sheet jam processing using the tab portion can be operated much easily. Further, the guide member never turns beyond the second position, to thereby prevent the user from braking the guide member by forcedly turning thereof.
It may be preferable that the tab portion has such a height that the top of the tab portion is below the top of the frame member when the guide member is in the first position.
In this case, an operation capability of the guide member can be ensured while the height of the tab portion is restricted to a necessity minimum. Further, it is not needed to ensure an unnecessary space for providing the tab portion so that the sheet conveying device can be more miniaturized.
The image forming apparatus according to an embodiment of the present invention includes the above mentioned sheet conveying device and the section detachably mounted above the guide member.
In the image forming apparatus, the sheet conveying device is mounted therein, and the section mounted above the guide member is detachable so that the user-friendly image forming apparatus in which the sheet jam processing is easily conducted can be realized.
It may be preferable that the section is the developing unit which forms the toner image on the photoconductive drum.
In this case, the space above the guide member is enough ensured by taking the developing unit off so that the sheet jam processing operation using the guide member can be conducted more easily.
This application is based on patent application No. 2005-250448 filed in Japan, the contents of which are hereby incorporated by references.
As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to embraced by the claims.
Number | Date | Country | Kind |
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2005-250448 | Aug 2005 | JP | national |