SHEET FEEDING DEVICE AND IMAGE FORMING APPARATUS

Abstract

A sheet feeding device includes a regulation member having a sheet-regulation surface, and an air blowing mechanism. The regulation member regulates the positions of sheets that are stacked on a sheet stacking device. The air blowing mechanism raises the sheets by blowing air onto an edge of a stack of the sheets that are stacked on the sheet stacking device. The regulation member is formed so that air that is blown from the air blowing mechanism passes the regulation member, thereby overcoming the problem of the flow of sheet-loosening air and sheet-separation air being disturbed by the regulation member.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding device and an image forming apparatus, and, more particularly, to a sheet feeding device and an image forming apparatus which feed sheets by separating the sheets as a result of blowing air onto the sheets.

2. Description of the Related Art

A related image forming apparatus, such as a copying machine or a printer, includes a sheet feeding device that feeds sheets to an image forming device by separating them one at a time from a topmost sheet of the sheets that are stacked on sheet stacking means.

One type of such a sheet feeding device feeds sheets by an air sheet-feeding method. In the method, air is blown onto an edge of a stack of sheets that are stacked on the sheet stacking means to raise the plurality of sheets and loosen them from each other. Then, the topmost sheet is attracted to an attracting conveying belt and fed. The sheet feeding device of the type that uses the air sheet-feeding method is, particularly, suited for high-speed sheet feeding, so that it is frequently used in high-speed apparatuses. For example, Japanese Patent Laid-Open No. 5-61305 discloses a sheet feeding device that uses the air sheet-feeding method.

FIG. 8 is a schematic sectional view of a related sheet feeding device that uses the air sheet-feeding method.

As shown in FIG. 8, a sheet-feed deck 401 that holds sheets P has a tray 403. The tray 403 is used to stack the sheets P therein and can be raised and lowered in accordance with the number of sheets. The sheets P are held at predetermined positions by side regulation plates 457, a rear-end regulation plate 458, and a front-end regulation plate 456. The side regulation plates 457 and the rear-end regulation plate 458 are movable in a sheet width direction and a sheet-feed direction so that they can be used with sheets of various sizes.

An attracting conveying belt 407 is provided above the sheet-feed deck 401, and can rotate in the sheet-feed direction that is indicated by an arrow in FIG. 8. The belt 407 attracts the topmost sheet of the sheets P that are stacked in the tray 403, and transports the topmost sheet downstream. A suction duct 492 that causes negative pressure to act for attracting the topmost sheet by suction air from a suction fan (not shown) is provided at an inner side of the attracting conveying belt 407.

A sheet-loosening air nozzle 494 is provided downstream from the sheet-feed deck 401. The air nozzle 494 is used to loosen a stack of sheets as a result of raising the stack of sheets by blowing air onto a front-side edge of the stack of sheets that are stacked in the tray 403. To prevent double feeding, a sheet-separation air nozzle 493 that supplies sheet-separation air for separating a next sheet from the topmost sheet that is attracted to the attracting conveying belt 407 is provided.

When feeding the sheets, the sheet feeding device having such a structure loosens the sheets as a result of blowing sheet-loosening air from the sheet-loosening air nozzle 494 onto the front-side edge of the stack of sheets. At the same time, suction air is made to act upon the topmost sheet to attract the topmost sheet to the attracting conveying belt 407. Further, the sheet-separation air from the air nozzle 493 separates the next sheet from the topmost sheet that is attracted to the attracting conveying belt 407.

The air from the sheet-loosening air nozzle 494 and the air from the sheet-separation air nozzle 493 cause a plurality of upper sheets of the stack of sheets to be raised and pushed rearward. However, the rearward movement of the upper sheets is stopped by the rear-end regulation plate 458. Accordingly, the rear-end regulation plate 458 has a height that does not allow the sheets that are moved rearward to move over the rear-end regulation plate 458. More specifically, the rear-end regulation plate 458 is at least higher than a surface of the attracting conveying belt 407 that attracts the sheets.

Rotating the attracting conveying belt 407 after attracting only the topmost sheet to the attracting conveying belt 407 makes it possible to transport topmost sheets one at a time and downstream by the attracting conveying belt 407 while preventing double feeding.

In the air sheet-feeding method, the air that is blown onto the edges of the sheets pass between the sheets of the sheet stack, so that the sheets are reliably raised and loosened. Accordingly, to reliably loosen the stack of sheets, the air needs to flow in a laminar state between the sheets of the sheet stack.

In the related sheet feeding device and image forming apparatus, when air that is blown onto and acting upon the sheets passes through the stack of sheets, and, then, strikes the rear-end regulation plate 458, a disturbance is produced in the flow of air, in which case, the air from the sheet-loosening air nozzle 494 and the air from the sheet-separation air nozzle 493 do not flow in a laminar state. As a result, the stack of sheets is not satisfactorily loosened and separated. This may result in double feeding or improper feeding.

SUMMARY OF THE INVENTION

In view of such circumstances, the present invention provides a sheet feeding device and an image forming apparatus which can efficiently loosen and separate sheets by air

According to the present invention, a sheet feeding device is provided which includes a tray adapted to support a stack of sheets, the tray further being adapted to be raised and lowered; a regulation member having a sheet-regulation surface, the regulation member being adapted to regulate the position of the sheet stack as a result of the sheet-regulation surface coming into contact with the sheet stack; an air blowing mechanism positioned opposing to the regulation member, wherein the air blowing mechanism is configured to blow air into an upper region of the sheet stack; and a sheet feeding mechanism adapted to feed the top-most sheet away from the sheet stack, wherein the regulation member is configured such that the blown air passes through an escape portion, defined by the sheet-regulation surface.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view of a printer, which is an example of an image forming apparatus, including a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a plan view of a paper deck that is provided at the sheet feeding device.

FIG. 3 is a side view of the paper deck.

FIGS. 4A and 4B show structures of a rear-end regulation plate that is provided at the paper deck.

FIGS. 5A and 5B illustrate an example in which through holes are formed in the rear-end regulation plate.

FIG. 6 illustrates an operation of the rear-end regulation plate having the through holes.

FIG. 7 illustrates a flow of air when feeding sheets by the sheet feeding device.

FIG. 8 illustrates a structure of a related sheet feeding device.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a schematic structural view of a printer, which is an example of an image forming apparatus, including a sheet feeding device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1000 denotes a printer, and reference numeral 1001 denotes a printer body. An image reading device 200 is provided at the upper portion of the printer body 1001, and reads an image of an original that is sent onto a platen glass 102, serving as an original table, by an automatic original feeding device 100. An image forming device 300 that forms images on sheets P, and a sheet feeding device 400 that supplies the sheets P to the image forming device 300 are provided below the image reading device 200. The sheet feeding device 400 uses the aforementioned air sheet-feeding method.

The image forming device 300 includes, for example, a photosensitive drum 111, a developing unit 112, and a laser scanner unit 110. The sheet feeding device 400 includes a first paper deck 401 and a second paper deck 451, which having a common sheet-feeding mechanism, and an attracting conveying belt 407, which is a sheet-feeding mechanism for feeding the sheets that are held in the first paper deck 401 and the second paper deck 451.

The sheet feeding device 400 includes air blowing units 406 which are air blowing mechanisms that are provided at a side towards which sheet stack supported by trays 403 are fed and that blow air from front-side edges of the sheet stack. The trays 403 are provided at the first paper deck 401 and the second paper deck 451, respectively, and will be described in more detail later. The first paper deck 401 can hold 1500 sheets P, and the second paper deck 451 can hold 2000 sheets P.

An image forming process of the printer 1000 having such a structure will be described.

When a start button (not shown) is pressed, the original feeding device 100 feeds upwardly facing originals, which are set in an original tray 150, leftwards one at a time starting from the first page. Then, it feeds the originals onto the platen glass 102 from the left of the platen glass 102 through a curved path to transport the originals towards the right via a feeding-and-reading position. Thereafter, the originals are discharged towards an external sheet-discharge tray 151.

When the originals pass the feeding-and-reading position at the platen glass 102 from left to right, the images of the originals are read by a scanner unit 104 that is held at a position which is in correspondence with the feeding-and-reading position. In general, this reading method is called an “original feeding-and-reading method.”

More specifically, when the originals pass the feeding-and-reading position, reading surfaces of the originals are irradiated with light of a lamp 103 of the scanner unit 104. Light that is reflected from the originals is guided to a lens 108 through mirrors 105, 106, and 107. Light that passes through the lens 108 is focused onto an imaging plane of an image sensor 109.

When the originals are transported so that they pass the feeding-and-reading position from left to right, the originals are scanned for reading the originals, with a direction that is perpendicular to a direction of transportation of the originals being defined as a main scanning direction and the transportation direction being defined as a sub-scanning direction.

More specifically, the entire images of the originals are optically read as a result of transporting the originals in the sub-scanning direction while the image sensor 109 reads the images of the originals one line at a time in the main scan direction when the originals pass the feeding-and-reading position. Then, the images that are optically read in this way are converted into image data by the image sensor 109, and the image data is transmitted to the laser scanner unit 110 of the image forming device through a memory (not shown).

The image reading device 200 can also read the originals as a result of causing the scanner unit 104 to perform scanning from left to light while the originals that are transported onto the platen glass 102 by the original feeding device 100 are stopped at predetermined positions. This reading method is called an “original fixing-and-reading method.”

When the originals are to be read without using the original feeding device 100, first, a user raises the original feeding device 100 and places the originals on the platen glass 102. Then, the user uses the scanner unit 104 to scan the originals from left to right, so that the originals are read. When the originals are read without using the original feeding device 100, the “original fixing-and-reading method” is performed.

Next, in the image forming device 300, when the image data is transmitted from the image reading device 200 to the laser scanner unit 110, the photosensitive drum 111 is irradiated with laser light on the basis of the image data from the laser scanner unit 110. At this time, the photosensitive drum 111 is previously charged. When the photosensitive drum 111 is irradiated with the laser light, an electrostatic latent image is formed. Then, the electrostatic latent image is developed by the developing unit 112 to form a toner image on the photosensitive drum 111.

When a sheet-feed signal is output to the sheet feeding device 400 from a controlling device (not shown), sheets P that are held in the first paper deck 401 or the second paper deck 451 are attracted to the attracting conveying belt 407 and sent out. Then, the sheets P that are sent out in this way pass through a sheet transportation unit 409, and is transported to registration rollers 115 to correct any oblique movement of the sheets P. Thereafter, the sheets P are sent to a transfer unit, including the photosensitive drum 111 and a transfer roller 116, in synchronization with the toner image on the photosensitive drum by the registration rollers 115.

Next, the toner image is transferred onto the sheet P that has been sent to the transfer unit in this way. Then, the sheet P having the toner image transferred thereon is transported to a fixing unit 117. Then, the transferred unfixed image is permanently fixed to the sheet P by heating and applying pressure to the image by the fixing unit 117. Thereafter, the sheet P having the image fixed thereto in this way is discharged by discharge rollers 118 and 120 to a sheet-discharge tray 119 or a sheet-discharge tray 121 from the printer body 101.

FIG. 2 is a plan view of the first paper deck 401. The second paper deck 451 structurally differs from the first paper deck 401 only in the maximum number of sheets that it can hold.

The first paper deck 401 includes a sheet holding unit 453 and the tray 403 serving as sheet stacking unit. The sheet holding unit 453 is used to set sheets P thereon. The tray 403 is provided in the sheet holding unit 453 so that it can be raised and lowered, and holds the sheets P in layers. A tray raising-and-lowering mechanism (not shown) moves the tray 403 to a lowered position for replenishing or replacing sheets and to a feeding position for sending out sheets.

The first paper deck 401 also includes side regulation plates 457 and a rear-end regulation plate 458. The side regulation plates 457 regulate the positions of the sheets P, supported by the tray 403, in a widthwise direction of the sheets P that is perpendicular to a sheet-feed direction of the sheets P. The rear-end regulation plate 458 regulates the rear-end positions of the sheets P at an upstream side in the sheet-feed direction of the sheets P. The side regulation plates 457 and the rear-end regulation plate 458, which regulate the positions of the sheets P, are formed so as to be movable in accordance with the size of the sheets P.

In the embodiment, sheets P having widths in the range of from B5R to 14.33 inches (182 mm to 364 mm) and lengths in the range of from B5 to 19.2 inches (182 mm to 488 mm) can be stacked.

To make it possible to stack the sheets P having such widths and lengths, notches 459 and 460 are provided in the tray 403 so as not to prevent the movement of the side regulation plates 457 and the rear-end regulation plate 458 in the range of movement of the side regulation plates 457 and the rear-end regulation plate 458.

In the paper deck on which the sheets P from small sheets P to large sheets P can be stacked, the location of the rear-end regulation plate 458 is positioned at about the center of the paper deck in the widthwise direction so as not to be provided at the notches 459 of the tray 403. The attracting conveying belt 407 and a suction duct 492 are also disposed at about the center of the paper duct in the sheet-width direction as shown in FIGS. 2 and 3 so as to allow sheets having the smallest length in the widthwise direction (B5R-size sheets in the embodiment) to be stacked.

As discussed in the description of the related art, air from the air blowing unit 406 causes a plurality of upper sheets of the stack of sheets to be raised and pushed rearward. However, the rearward movement of the upper sheets is stopped by the rear-end regulation plate 458. Accordingly, the rear-end regulation plate 458 has a height that does not allow the sheets that are moved rearward to move over the rear-end regulation plate 458. More specifically, the rear-end regulation plate 458 is at least higher than a surface of the attracting conveying belt 407 that attracts the sheets.

Further, as shown in FIG. 3, sheet-loosening air nozzles 493 for blowing out sheet-loosening air to loosen the sheets P and sheet-separation air nozzles 494 for blowing out sheet-separation air to prevent double feeding are provided in the air blowing unit 406 so as to be situated in the center thereof in the widthwise direction.

In particular, the sheet-separation air nozzles 493 are for separating a next sheet from the top-most sheet that is attracted to the attracting conveying belt 407. It is preferred that the sheet-separation air nozzles 493 need be disposed at or about the same positions in the widthwise direction as an opening of the suction duct 492 and the attracting conveying belt 407.

The separation and loosening of the sheets are performed more effectively when a plurality of the air nozzles 493 and a plurality of air nozzles 494 are provided than when only one air nozzle 493 and one air nozzle 494 are provided. Therefore, in the embodiment, as shown in FIG. 3, six sheet-separation air nozzles 493 and two sheet-loosening air nozzles 494 are provided at the central portion of the paper deck in the widthwise direction.

When the first paper deck 401 has such a structure, as shown in FIG. 2, the center of the sheet-separation air nozzles 493 and the rear-end regulation plate 458 overlap each other in the sheet-feed direction. This means that the rear-end regulation plate 458 is provided so as to oppose the sheet-separation air nozzles 493. For this reason, after air from the sheet-separation air nozzles 493 flows through the sheets while the air acts upon the sheets, the air flows towards the rear-end regulation plate 458.

In the embodiment, as shown in FIG. 4A, an escape portion 481, which is formed by cutting away a portion of a sheet-regulation surface 458a opposing the sheet-separation air nozzles 493, is provided. The sheet-regulation surface 458a is a surface of the rear-end regulation plate 458 that comes into contact with a rear edge of a sheet 491 (see FIG. 7). The escape portion 481 allows air flowing towards the rear-end regulation plate 458 after being blown out from the sheet-separation nozzles 493 and passing through the sheets 491 to escape. Therefore, no disturbance is produced in the air, so that the air is in an ideal laminar state as shown in FIG. 7.

As shown in FIG. 4A, when through holes (escape portion) 481a are formed in the sheet-regulation surface 458a, the air passes the rear-end regulation plate 458 from the through holes 481a, so that the laminar state is more effectively produced.

When the escape portion 481 is provided in the rear-end regulation member 458 so that the air from the sheet-separation air nozzles 493 passes the rear-end regulation member 458, the problem of the rear-end regulation plate 458 disturbing the flow of the sheet-loosening air and the sheet-separation air can be prevented from occurring. Therefore, it is possible to produce a laminar flow of blown air, and to efficiently loosen and separate the sheets P by the air without loss of air.

In the embodiment, the escape portion 481 is provided by cutting away a portion of the sheet-regulation surface 458a of the rear-end regulation plate 458 that opposes the sheet-separation air nozzles 493. However, when the rear-end regulation plate 458 has a portion that opposes the sheet-loosening air nozzles 494 due to the shape of the rear-end regulation plate 458, the escape portion 481 may be provided by cutting a portion of the sheet-regulation surface 458a that opposes the sheet-loosening air nozzles 494.

To cause the air to pass the rear-end regulation member 458 from the air blowing unit 406, as shown in FIG. 4B, an escape portion 481b may be formed as a result of providing the sheet-regulation surface 458a of the rear-end regulation plate 458 at a location that does not oppose the air blowing unit 406.

Accordingly, when the rear-end regulation plate 458 is formed into a shape or is disposed at a location that does not block the air that is blown out from the sheet-separation air nozzles 493 or the sheet-loosening air nozzles 494 of the air blowing unit 406, it is possible to smoothen the flow of air.

Next, the example in which the through holes (escape portion) 481a, instead of the escape portion 481b, are formed in the rear-end regulation plate 458 will be described. As shown in FIGS. 5A and 5B, a retreating member 481 is provided at a top portion of the rear-end regulation plate 458 that is provided at the first paper deck 401.

The retreating member 481 is guided by a guiding member 458b so as to slide obliquely at an angle of 45 degrees with respect to the rear-end regulation plate 458. A retreating spring 482 is disposed between the rear-end regulation plate 458 and the retreating member 481. One end 482a of the retreating spring 482 is stopped by the body 458a of the rear-end regulation plate 458, and another end 482b of the retreating spring 482 is stopped by the retreating member 481.

As shown in FIG. 5A, by the action of the retreating spring 482, the retreating member 481 is extended upward. When, for example, an obstacle, such as the frame 151 of the sheet feeding device 400, exists as shown in FIG. 6, the retreating member 481 retreats by being pushed downward by the obstacle as shown in FIG. 5B.

Here, as shown in FIGS. 5A and 5B, the retreating member 481 has the through holes 481a that pass through the retreating member 481 in a front-back direction. The through holes 481a allow the air from the sheet-separation nozzles 493 and the air from the sheet-loosening air nozzles 494 to flow smoothly between the sheets.

Accordingly, it is possible to cause the air to flow in a laminar state between the sheets that exist between the nozzles 493 and the rear-end regulation plate 458 and between the nozzles 494 and the rear-end regulation plate 458. The laminar flow of the air makes it possible to perform sheet loosening and separation with higher efficiency.

When the rear-end regulation plate 458 is positioned at a location opposing the locations of the nozzles 493 and 494, that is, at a location opposing the openings of the nozzles 493 and 494 in the sheet-feed direction, the through holes 481a make it possible to perform sheet loosening and separation with even higher efficiency.

In the foregoing description, the rear-end regulation plate 458 is used as a regulation member that regulates the positions of the sheets, and the air blowing units 406 blow air from the front edges of sheet stack that are stacked in the trays 403. However, the present invention is not limited thereto. For example, when air is blown from side edges of the sheet stack that are stacked in the trays 403, escape portions 481 or through holes 481a may be formed in the side regulation plates 458 that regulate the positions of the side edges of the sheets.

Although, in the embodiment, the regulation member has an escape portion 481 and through holes 481a, the regulation member may have an escape portion 481b and through holes 481a.

Although, in the embodiment, the sheet feeding unit transports sheets as a result of attracting the sheets to the attracting conveying belt 407, the present invention is not limited thereto. For example, the sheet feeding unit may be one that blows air onto the side edges of the sheet stack for previously loosening the sheets to reliably feed the sheets when the sheets are separated by a sheet separating method other than that described above, such as a typical sheet separating method that uses a reversing roller.

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 modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No. 2006-093634 filed Mar. 30, 2006, which is hereby incorporated by reference herein in its entirety.

Claims

1. A sheet feeding device comprising:

a tray adapted to support a stack of sheets, the tray further being adapted to be raised and lowered;

a regulation member having a sheet-regulation surface, the regulation member being adapted to regulate the position of the sheet stack as a result of the sheet-regulation surface coming into contact with the sheet stack;

an air blowing mechanism positioned opposing to the regulation member, wherein the air blowing mechanism is configured to blow air into an upper region of the sheet stack; and

a sheet feeding mechanism adapted to feed the top-most sheet away from the sheet stack,

wherein the regulation member is configured such that the blown air passes through an escape portion, defined by the sheet-regulation surface.

2. The sheet feeding device according to claim 1, wherein the escape portion faces, in an opposing manner, the air blowing mechanism.

3. The sheet feeding device according to claim 1, wherein the escape portion of the sheet-regulation member defines at least one through hole, at a location that faces the air blowing mechanism in an opposing manner, the through hole configured to allow the blown air to pass there through such that the air passes through the regulation member.

4. The sheet feeding device according to claim 1, wherein escape portion is generally U-shaped and positioned at an upper portion of the sheet-regulation surface.

5. The sheet feeding device according to claim 1, wherein the air blowing mechanism has a plurality of nozzles for blowing the air from the upper region of the sheet stack towards the regulation member.

6. An image forming apparatus comprising:

a tray adapted to support a stack of sheets, the tray further adapted to be raised and lowered;

a regulation member having a sheet-regulation surface, the regulation member being adapted to regulate the position of the sheet stack as a result of the sheet-regulation surface coming into contact with the sheet stack;

an air blowing mechanism positioned opposing to the regulation member, wherein the air blowing mechanism is configured to blow air into an upper region of the sheet stack;

a sheet feeding mechanism adapted to feed the top-most sheet away from the sheet stack; and

an image forming device that forms images on the sheets fed by the sheet feeding mechanism,

wherein the regulation member is configured such that the blown air passes through an escape portion, defined by the sheet-regulation surface.