This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2011-274864 filed on Dec. 15, 2011, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus and more particularly to an image forming apparatus provided with a sheet feeding device configured to separate sheets one by one from stacked sheets and convey each sheet to an image forming section.
2. Description of Related Art
Some image forming apparatus each include an image forming section to form an image on a sheet and a sheet feeding device (feeder) to feed the sheet to the image forming section. Many of sheet feeding devices are each provided with a separating mechanism for separating sheets one by one from stacked sheets to feed one sheet each.
For example, JP-A-3(1991)-51230 discloses a sheet feeding device configured to rotate a separating roller in a reverse direction (see an arrow Tb in FIG. 1 of JP-A-3(1991)-51230) and thereafter rotate the separating roller in a forward (normal) direction (see an arrow Ta in FIG. 1 of JP-A-3(1991)-51230) to convey a sheet. This is to separate an uppermost sheet from stacked sheets and convey the sheet along a sheet conveying path. JP-A-2002-87606 discloses a sheet feeding device including an auxiliary roller which rotates in a reverse direction and thereafter rotates in a forward direction (see FIG. 2 and others in JP-A-2002-87606). This is to prevent double sheet feeding.
In recent years, meanwhile, there has been an increasing demand for downsizing of an image forming apparatus to address environmental issues or save office space. However, the width of a conventional image forming apparatus is, as shown in
The present invention has been made to solve the above conventional problems and has a purpose to provide an image forming apparatus including a sheet feeding device configured to sequentially feed sheets one by one from stacked sheets and ensure a reduced width of the image forming apparatus.
To achieve the above purpose, one aspect of the invention provides an image forming apparatus comprising: a sheet cassette configured to accommodate stacked sheets; a separating member configured to separate an uppermost sheet from the stacked sheets accommodated in the sheet cassette; a sheet feed roller configured to feed the uppermost sheet from the stacked sheets accommodated in the sheet cassette; an image forming section configured to form an image on the sheet fed from the sheet cassette; and a sheet conveying path placed between the sheet cassette and the image forming section, wherein the image forming section and the sheet conveying path are placed in a position within a width of the sheet cassette defined between a front end and a rear end of the cassette in a sheet feeding direction and above the sheet cassette, the separating member has a tip to be placed to contact with a portion of the stacked sheets accommodated in the sheet cassette between the front end and the rear end of the cassette, and the sheet feed roller is placed in a position between the front end and the rear end of the sheet cassette and apart from the tip of the separating member toward the rear end of the sheet cassette. In this image forming apparatus, the overall or full width of the image forming apparatus does not greatly differ from the width of the sheet cassette. That is, downsizing of the image forming apparatus is achieved.
According to the present invention, there is provided an image forming apparatus including a sheet feeding device configured to sequentially feed sheets one by one from stacked sheets and ensure a reduced width of an image forming apparatus.
A detailed description of a preferred embodiment of the present invention will now be given referring to the accompanying drawings. In the present embodiment, the invention is applied to a black and white printer.
An image forming apparatus 100 is a black and white printer having a schematic configuration shown in
The sheet cassette 10 is arranged to accommodate stacked sheets and feed an uppermost sheet from the stacked sheets. A fed sheet is conveyed along the sheet conveying path 20 to the image forming section 30. The details of this configuration will be explained later. The sheet cassette 10 can be pulled out to the front side (near side) in
The sheet feed roller 14 is used to pick up and feed an uppermost sheet from stacked sheets loaded in the sheet cassette 10 toward the sheet conveying path 20. This sheet conveying path 20 is arranged to convey the sheet fed out from the cassette 10 toward the image forming section 30. The sheet conveying path 20 is provided with a timing sensor 21 to determine the timing at which a sheet is fed to the transfer roller 40. The sheet conveying path 20 is located in a position within the width W1 of the cassette 10 and above the cassette 10. Accordingly, the full width W of the image forming apparatus 100 in the present embodiment is not so greatly different from the width W1 of the cassette 10. In other words, the image forming apparatus 100 in the present embodiment is smaller in size than the conventional image forming apparatus.
The image forming section 30 is arranged to form an image on a sheet. This image forming section 30 includes a photoconductor drum 31, a charging unit 32, an exposing unit 33, and a developing unit 34, and a cleaner 35. The photoconductor drum 31 is an image carrier to carry a toner image thereon. This drum 31 is therefore rotated in a direction indicated by an arrow D2 in
The transfer roller 40 is a transfer member for transferring a toner image formed on the photoconductor drum 31 to a sheet. The sheet having the toner image transferred thereon is then transported along the sheet conveying path 20 in a direction indicated by an arrow D1 in
The fixing unit 50 is arranged to fix the transferred toner image on the sheet. The pair of discharging rollers 61 are arranged to discharge the sheet having the toner image fixed thereon to the discharge tray 62. This tray 62 is a tray for receiving the sheet having the toner image fixed thereon.
The motor M is a drive source to drive the photoconductor drum 31 and various rollers to rotate. The sheet feed roller 14 and conveying rollers 17 mentioned later are to be driven by the motor M. Each component such as the drum 31 is also to be driven by the motor M. These components are rotated in sync with the rotation of the motor M. However, the rotation speeds of the components are not necessary equal to each other because of the use of a reduction gear or the like. The controller 90 is configured to control the operation of each component of the image forming section 30 and the rotation of the motor M.
As shown in
2-1. Configuration of Sheet Feed Cassette
The configuration of the sheet cassette 10 will be explained below.
The cassette body 11 is a sheet feed case for accommodating stacked sheets P. The cassette body 11 has a bottom plate 11a, a front end portion 11T, and a rear end portion 11E. The front end portion 11T is a side wall of the cassette body 11 on a side facing the leading end PT of the sheet P1 before conveyance (in a loaded state). The rear end portion 11E is a side wall of the cassette body 11 on the other side facing the rear end PE of the sheet P1 before conveyance (in the loaded state).
The rear end portion 11E of the cassette body 11 includes a slanted surface 11b. This slanted surface 11b is slanted from the bottom plate 11a to an upper end of the rear end portion 11E so that the rear end portion 11E is more apart from the front end portion 11T of the cassette body 11 with distance from the bottom plate 11a. The slanted surface 11b can function, as mentioned later, to guide the sheet P1 moved back by the sheet feed roller 14 to be warped or curved upward from the sheet cassette 10. The lifting spring 12 is arranged to lift up the portions of the stacked sheets P near the leading end PT by way of the lifting plate 13. This lifting plate 13 is a sheet loading section to actually load thereon the stacked sheets P.
2-2. Sheet Feed Roller, Guide Member, and others
The sheet feeding device includes the sheet feed roller 14 and the guide member 15 in addition to the sheet cassette 10. The sheet feed roller 14 and the guide member 15 are provided in a main body of the image forming apparatus 100 and are not allowed to be pulled out together with the sheet cassette 10. The sheet feed roller 14 is placed in a position upstream from the guide member 15 and a separating blade 16 mentioned later in a sheet conveying path. Further, the sheet feed roller 14 is located between the front end portion 11T and the rear end portion 11E of the cassette body 11 and somewhat apart from the tip of the separating blade 16 toward the rear end portion 11E. The sheet feed roller 14 is configured to, under the control of the controller 90, rotate in a forward (normal) direction (indicated by an arrow DN in
The guide member 15 is an element for guiding conveyance of the sheet P1 toward the sheet conveying path 20. The guide member 15 includes the separating blade 16 and the conveying rollers 17a, 17b. The blade 16 is attached to the leading end of the guide member 15 and serves as a separating element for picking up and separating the sheet P1 from the stacked sheets P. The blade 16 is placed in such a manner that the tip of the blade 16 is in contact with an uppermost surface of the stacked sheets P between the front end portion 11T and the rear end portion 11E of the cassette body 11. The conveying rollers 17a, 17b are arranged on the end portion of the guide member 15 opposite to the separating blade 16. The conveying rollers 17a, 17b serve to feed the sheet P1 fed by the sheet feed roller 14 to the sheet conveying path 20.
The guide member 15 is provided with a press-contact spring 18 that pulls the guide member 15 to swing, thereby swinging the separating blade 16 together, so that the tip of the blade 16 is urged in press-contact with the stacked sheets P in a thickness direction thereof. Unless the blade 16 presses against the stacked sheets P, there is a risk that the leading end PT of the sheet P1 moved back by the sheet feed roller 14 as mentioned later may go under the blade 16 when the sheet P1 is thereafter moved forward. It is to be noted that the press-contact spring 18 is not illustrated in
2-3. Configuration of Guide Member
The guide member 15 and the separating blade 16 are each made of a resin film such as polyester film or polyethylene film. Instead, they may be made of stainless sheet or steel sheet. The blade 16 may also be made of a material with a high friction coefficient or designed in a shape subjected to surface finishing to provide a high friction coefficient. This is because such a separating blade 16 can easily separate the sheet P1 from the stacked sheets P.
A sheet feeding operation carried out in the sheet feeding device will be explained below. As shown in
Subsequently, the sheet feed roller 14 is rotated in the direction indicated with the arrow DN (forward rotation) in
As shown in
The number of stacked sheets P loaded on the sheet cassette 10 decreases every time image formation. Thus, the following explanation is given to changes in the angle of the separating blade 16 according to the amount of sheets loaded in the sheet cassette 10.
4-1. Full Loaded Condition
4-2. Empty Condition
As explained in detail above, the sheet conveying path 20 is placed within the range of the sheet cassette 10 in the width direction and above the cassette 10. Thus, the full width of the image forming apparatus 100 in the present embodiment is not so greatly different from the width of the sheet cassette 10. That is, the size of the image forming apparatus 100 in the present embodiment is smaller than the size of the conventional image forming apparatus.
5-1. Shape of Cassette Body
Modified examples of the present embodiment are explained below.
Although the above embodiment provides the slanted surface 11b in the cassette body 11, the slanted surface 11b is not necessarily provided. As shown in
As shown in
5-2. Shape of Lifting Plate
As shown in
5-3. High Friction Member
As shown in
As explained in detail above, the image forming apparatus 100 in the embodiment is configured such that the sheet feed roller 14 and the separating blade 16 to convey the sheet P1 to the section above the cassette body 11 are provided within the width W1 of the sheet cassette 10. Accordingly, there is realized the image forming apparatus 100 capable of feeding each sheet P1 sequentially from the stacked sheets P and conveying the sheet P1 to the sheet conveying path 20 located above the cassette 10.
In the image forming apparatus 100 in the embodiment, the sheet conveying path 20 is also placed in the upper section within the width W1 of the sheet cassette 10. Thus, the full width W of the image forming apparatus 100 is not so greatly different from the width W1 of the sheet cassette 10. That is, the image forming apparatus 100 is smaller in size than the conventional image forming apparatus. Such a size-reduced image forming apparatus can be achieved.
The above embodiments are mere examples not limiting the invention thereto. The present invention may be embodied in other specific forms without departing from the essential characteristics thereof. For instance, the invention is not limited to the black and white printer, but alternatively may be a color printer. Further, the invention is applicable to a copying machine as well as the printer. The invention can be applied to an image reading apparatus and an image forming apparatus configured to transmit/receive print jobs through public lines, and a combination machine. Moreover, the invention is applicable to any type of apparatus regardless of the kinds of toner and also to an image forming apparatus using a liquid color forming agent instead of toner. The guide member 15 and the separating blade 16 may be provided as an integral single piece.
The aforementioned image forming apparatus preferably includes a sheet feed roller controller configured to control the sheet feed roller to rotate reversely to feed the uppermost sheet of the stacked sheets in a direction opposite to the sheet conveying path and thereafter rotate forwardly to feed the sheet in a direction toward the sheet conveying path. This makes it possible to appropriately feed an uppermost sheet from stacked sheets.
In the aforementioned image forming apparatus, preferably, an amount of reverse rotation of the sheet feed roller to be controlled by the sheet feed roller controller is determined to an amount of rotation at which a leading end of a sheet is moved to a position between the tip of the separating member and the sheet feed roller. Thus, each sheet can be temporarily moved back to be appropriately separated from the stacked sheets, and fed forward one by one.
The aforementioned image forming apparatus preferably includes a press-contact member configured to bring the tip of the separating member into press-contact with the uppermost sheet of the stacked sheets accommodated in the sheet cassette. This configuration can prevent the leading end of each sheet to be fed from going under the separating member.
The aforementioned image forming apparatus preferably includes a conveying roller configured to convey the sheet toward the sheet conveying path, the sheet having been fed by the sheet feed roller from the stacked sheets accommodated in the sheet cassette and separated by the separating member. The separated sheet is thus delivered into the sheet conveying path.
In the aforementioned image forming apparatus, preferably, there is provided a guide member holding the separating member at one end, the guide member being configured to be rotatable about a position (axis) opposite to the separating member and to feed the sheet separated by the separating member toward the sheet conveying path, wherein the conveying roller is provided at the other end of the guide member opposite to the separating member. Thus, the separated sheet can be directed to the sheet conveying path irrespective of the amount of sheets in the sheet cassette.
The aforementioned image forming apparatus preferably includes a conveying roller controller configured to control the conveying roller to start rotation to convey the sheet toward the sheet conveying path before the leading end of the uppermost sheet of the stacked sheets accommodated in the sheet cassette reaches the conveying roller. Thus, the separated sheet can be reliably delivered into the sheet conveying path. The rotation of the conveying roller may also be started after the forward rotation of the sheet feed roller is started.
In the image forming apparatus, preferably, the sheet cassette includes a lifting plate having a bent or curved shape to load the stacked sheets in the form of an upward convex curve. This configuration makes it easy to separate an uppermost sheet from the stacked sheets.
In the image forming apparatus, preferably, the sheet cassette includes a slanted surface at the rear end, the slanted surface being so slanted as to be more apart from the front end of the sheet cassette with distance from a bottom plate of the sheet cassette. Accordingly, it is possible to prevent a sheet temporarily moved back from being folded.
In the image forming apparatus, preferably, the slanted surface is made of a high friction member having a larger friction coefficient than a material forming other portions of the sheet cassette than the slanted surface, so that separation of each sheet can be performed adequately.
The high friction member may include cork or rubber.
Number | Date | Country | Kind |
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2011-274864 | Dec 2011 | JP | national |