PAPER FEED APPARATUS

Abstract

In one embodiment of the invention, in a paper feed apparatus having a half-moon roller disposed above a plurality of sheets of paper stored in a stacked manner, and an auxiliary roller provided along one end of a half-circumferential face of the half-moon roller, the half-moon roller being rotated in a state in which a topmost sheet of paper has been put in contact with a height regulating member due to the sheets of paper being biased upward, so that the auxiliary roller and the half-circumferential face of the half-moon roller are successively pushed against the topmost sheet of paper, and while the sheets of paper are pushed down by the auxiliary roller or the half-circumferential face of the half-moon roller, the topmost sheet of paper is pulled out by the half-circumferential face of the half-moon roller: the one end of the half-circumferential face of the half-moon roller is separated from the auxiliary roller, and a curvature of the one end of the half-circumferential face is gradually increased closer to the auxiliary roller.

Description

BACKGROUND OF THE INVENTION

This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2008-185078 filed in Japan on Jul. 16, 2008, the entire contents of which are herein incorporated by reference.

The present invention relates to a paper feed apparatus that is applied in an image forming apparatus such as a copier, a printer, or a facsimile apparatus, for example, and feeds recording paper or the like.

JP S62-191337A discloses this type of conventional paper feed apparatus. Here, a bottom plate on which a plurality of sheets of paper are stored in a stacked manner is biased upward, and the sheets of paper are stored in a state in which the topmost sheet of paper is abutted against a height regulating member. A half-moon roller disposed above the sheets of paper is rotated so that the half-circumferential face of the half-moon roller pushes against the topmost sheet of paper, and the topmost sheet of paper is pulled out by the half-circumferential face of the half-moon roller.

Also, in the disclosure of JP H5-286585A, an auxiliary roller is additionally provided at the end of the half-circumferential face of the half-moon roller. By rotating the half-moon roller, the half-circumferential face of the half-moon roller is pushed against the topmost sheet of paper and the topmost sheet of paper is pulled out by the half-circumferential face of the half-moon roller. When the half-circumferential face of the half-moon roller is separated from the topmost sheet of paper, the auxiliary roller, which rotates together with the half-moon roller, is pushed against the topmost sheet of paper, pushing down the sheets of paper.

There is also a conventional apparatus as shown in FIG. 7. In this apparatus, an auxiliary roller 202 is provided in the vicinity of a half-circumferential face end 201a of a half-moon roller 201. As shown in FIG. 8, the half-moon roller 201 is rotated so that the auxiliary roller 202 and the half-circumferential face of the half-moon roller 201 successively push against a topmost sheet of paper 204, while the sheets of paper are pushed down by the auxiliary roller 202 or the half-circumferential face of the half-moon roller 201 so that the topmost sheet of paper 204 is separated downward from a height regulating member 203, the topmost sheet of paper 204 is pulled out by the half-circumferential face of the half-moon roller 201.

Various conventional apparatuses that employ a half-moon roller in this way have been provided.

Incidentally, in the conventional apparatus in FIGS. 7 and 8, a 90 degree corner is formed in the half-circumferential face end 201a of the half-moon roller 201, and because the half-circumferential face end 201a drops precipitously, when the auxiliary roller 202 and the half-circumferential face of the half-moon roller 201 are successively pushed against the topmost sheet of paper 204, the time during which the auxiliary roller 202 and the half-circumferential face of the half-moon roller 201 both are in contact with the topmost sheet of paper 204 is extremely short, and at about the same time that the auxiliary roller 202 separates from the topmost sheet of paper 204, the corner of the half-circumferential face end 201a of the half-moon roller 201 is pressed against the topmost sheet of paper 204. At this time, the topmost sheet of paper 204 is static, and the topmost sheet of paper 204 is locally pushed against by the corner of the half-circumferential face end 201a of the half-moon roller 201, and the static frictional force between the topmost sheet of paper 204 and the sheet of paper below the sheet of paper 204 becomes very high. Therefore, paper multi-feeding occurs in which when the topmost sheet of paper 204 is pulled out by the half-circumferential face of the half-moon roller 201, the sheet of paper below the sheet of paper 204 is also pulled out at the same time.

SUMMARY OF THE INVENTION

The present invention was made in consideration of the above problems, and it is an object thereof to provide a paper feed apparatus in which paper multi-feeding does not occur in a configuration in which an auxiliary roller is provided at an end of a half-circumferential face of a half-moon roller.

In order to address the above problems, the invention provides a paper feed apparatus having a half-moon roller disposed above a plurality of sheets of paper stored in a stacked manner, and an auxiliary roller provided along one end of a half-circumferential face of the half-moon roller, the half-moon roller being rotated in a state in which a topmost sheet of paper has been put in contact with a height regulating member due to the sheets of paper being biased upward, so that the auxiliary roller and the half-circumferential face of the half-moon roller are successively pushed against the topmost sheet of paper, and while the sheets of paper are pushed down by the auxiliary roller or the half-circumferential face of the half-moon roller, the topmost sheet of paper is pulled out by the half-circumferential face of the half-moon roller: the one end of the half-circumferential face of the half-moon roller being separated from the auxiliary roller, and a curvature of the one end of the half-circumferential face being gradually increased closer to the auxiliary roller. Also, in the paper feed apparatus with the above configuration, before the auxiliary roller separates from the surface of the topmost sheet of paper, the one end of the half-circumferential face of the half-moon roller having a large curvature presses against the surface of the topmost sheet of paper. Further, in the paper feed apparatus with the above configuration, the half-circumferential face of the half-moon roller is configured with a frictional face. Furthermore, in the paper feed apparatus with the above configuration, the half-moon roller is configured from a frame body that has been fixed to a shaft that serves as a rotational center of the half-moon roller, and a friction rubber that has been overlaid on the half-circumferential face of the frame body, the auxiliary roller being rotatably linked to one end of the frame body, and the half-circumferential face of the half-moon roller is the outside surface of the friction rubber, and the one end of the half-circumferential face of the half-moon roller is part of the friction rubber.

According to the invention having this sort of configuration, the one end of the half-circumferential face of the half-moon roller is separated from the auxiliary roller, and the curvature of the one end of the half-circumferential face is gradually increased closer to the auxiliary roller, so from before the auxiliary roller separates from the topmost sheet of paper, the half-circumferential face end of the half-moon roller gradually starts to be pushed against the topmost sheet of paper, thus increasing the time that both the auxiliary roller and the end of the half-circumferential face of the half-moon roller are in contact with the topmost sheet of paper. Therefore, the restoring force in the upward direction of the sheets of paper is received in a dispersed manner at the auxiliary roller and the end of the half-circumferential face of the half-moon roller, and the static frictional force between the topmost sheet of paper and the sheet of paper below the topmost sheet of paper decreases. In this state, pulling out of the topmost sheet of paper by the end of the half-circumferential face of the half-moon roller is started, and only this topmost sheet of paper is quickly pulled out, so paper multi-feeding is unlikely to occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view that shows an image forming apparatus in which one embodiment of a paper feed apparatus of the invention is applied.

FIG. 2 is a cross-sectional view that shows the paper feed apparatus of this embodiment.

FIG. 3 is a cross-sectional view that shows an enlarged view of the vicinity of a half-moon roller in the paper feed apparatus in FIG. 2.

FIG. 4 is a cross-sectional view that shows a state in which the half-moon roller in the paper feed apparatus in FIG. 2 has rotated approximately 90 degrees in the counter-clockwise direction.

FIG. 5 is a cross-sectional view that shows a further enlarged view of the vicinity of one end of the half-moon roller and an auxiliary roller.

FIG. 6 shows a process of displacement of the surface of a topmost sheet of paper relative to the half-moon roller and the auxiliary roller.

FIG. 7 is a cross-sectional view that shows an enlarged view of the vicinity of a half-moon roller in a conventional paper feed apparatus.

FIG. 8 is a cross-sectional view that shows a state in which the half-moon roller in the paper feed apparatus in FIG. 7 has rotated approximately 90 degrees in the counter-clockwise direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the invention will be described in detail with reference to the attached drawings.

FIG. 1 is a schematic view that shows an image forming apparatus in which one embodiment of a paper feed apparatus of the invention is applied. This image forming apparatus, acquires image data that has been read from an original, or acquires image data that has been received from outside, and forms a monochrome image represented by this image data on paper. Broadly speaking, this configuration includes an automatic document feeder (ADF) 101, an original reading apparatus 102, a printer unit 103, a paper transport unit 104, and a paper feed apparatus 105.

In the automatic document feeder 101, when an original of at least one sheet is placed on an original placement tray 11, the original is pulled out from the original placement tray 11 sheet by sheet and conveyed so that this original is guided to and passed over a first glass platen 14 of the original reading apparatus 102, and then the original is discharged to a discharge tray 12.

In the original reading apparatus 102, an optical unit including a first scanning unit 15 and a second scanning unit is disposed below the first glass platen 14, and when the original passes over the first glass platen 14, the original surface is exposed to light by a light source of the first scanning unit 15, reflected light from the original surface is guided to an imaging lens 17 by mirrors of the first scanning unit 15 and the second scanning unit 16, and an image of the original surface is formed on a CCD (Charge Coupled Device) 18 by the imaging lens 17. The CCD 18 repeatedly reads the image of the original surface in a main scanning direction, and outputs image data that represents the image of the original surface.

Also, when an original has been placed on a second glass platen 19 on the upper face of the original reading apparatus 102, while moving the first scanning unit 15 and the second scanning unit 16 in a sub-scanning direction, the original surface on the second glass platen 19 is exposed to light by the first scanning unit 15, reflected light from the original surface is further reflected and guided to the imaging lens 17 by the first scanning unit 15 and the second scanning unit 16, and an image of the original surface is formed on the CCD 18 by the imaging lens 17. At this time, the first scanning unit 15 and the second scanning unit 16 are moved while maintaining a predetermined speed relative to each other, so that the positional relationship of the first scanning unit 15 and the second scanning unit 16 is always maintained such that the length of a light path of reflected light, i.e., from the original surface to the first and second scanning units 15 and 16 to the imaging lens 17 to the CCD 18, does not change, and thus focus of the image of the original surface on the CCD 18 is always precisely maintained.

After a control circuit of a microcomputer or the like performs various image processing on the image data that has been output from the CCD 18, the image data is output to the printer unit 103.

Accordingly, in the original reading apparatus 102 of this embodiment, an original transport system in which an original is conveyed on the first glass platen 14, and an original fixed system in which an original is placed on the second glass platen 19, and then the optical unit (the first scanning unit 15 and the second scanning unit 16) is moved, are both employed.

A photosensitive drum 4 is disposed in approximately the middle of the printer unit 103, and around the photosensitive drum 4 are disposed a charging unit 5, an optical scanning unit 6, a development unit 7, a transfer unit 8, and a cleaning unit 9.

The charging unit 5 uniformly charges the surface of the photosensitive drum 4. The optical scanning unit 6 inputs image data, and while modulating the strength of an optical beam according to the image data, scans the optical beam on the uniformly charged photosensitive drum 4 to write an electrostatic latent image on the photosensitive drum 4. The development unit 7 develops the electrostatic latent image on the photosensitive drum 4 using a developer, thus forming a developed image on the photosensitive drum 4. The transfer unit 8, while conveying paper sandwiched between the transfer unit 8 and the photosensitive drum 4, transfers the developed image on the photosensitive drum 4 onto paper. The cleaning unit 9 removes developer remaining on the photosensitive drum 4, making it possible to form a new developed image on the photosensitive drum 4.

A fixing apparatus 20 is disposed in the upper part of the printer unit 103. The fixing apparatus 20 receives paper on which an image has been transferred, and sandwiching that paper between a fixing roller and a pressure roller, fixes the developed image that has been transferred onto the paper.

This paper is conveyed upward by a transport roller, and discharged to a discharge tray 22 from a discharge roller 21.

Also, when forming an image on both faces of paper, the paper is reverse-conveyed in the opposite direction by the discharge roller 21, and further conveyed to a reverse transport path 23, and after reversing the front and back sides of that paper, the paper is again conveyed to the printer unit 103, and a developed image is transferred and fixed to the back side of that paper. Then the paper is discharged from the discharge roller 21 to the discharge tray 22.

The paper feed apparatus 105 is provided with a paper feed cassette 24. Paper is separated and supplied sheet by sheet from the paper feed cassette 24, and supplied between the photosensitive drum 4 and the transfer unit 8, where the developed image on the photosensitive drum 4 is transferred to this paper.

Next is a detailed description of the paper feed apparatus 105 of this embodiment with reference to FIG. 2. In this paper feed apparatus 105, the paper feed cassette 24 is supported so as to be capable of sliding to the front side of the body of the image forming apparatus. The paper feed cassette 24 is pulled out to the front side, and a batch of paper is stored stacked on a bottom plate 31 inside of the paper feed cassette 24. A rear edge regulating member 32 supported so as to be capable of moving left-right in FIG. 2 is provided on the floor of the paper feed cassette 24. The front edge of the paper batch on the bottom plate 31 is put in contact with an inner wall face 24a of the paper feed cassette 24, the rear edge regulating member 32 is moved until abutting against the rear edge of the paper batch on the bottom plate 31, and the paper batch on the bottom plate 31 is positioned sandwiched between the inner wall face 24a and the rear edge regulating member 32. Also, both sides of the paper batch are positioned sandwiched by a pair of guide members (not shown) provided so as to be movable on the floor of the paper feed cassette 24.

Furthermore, the bottom plate 31 is axially supported by a shaft 31a, and is biased in the counter-clockwise direction around the shaft 31a by an unshown spring. The paper batch on the bottom plate 31 is raised upward until a topmost sheet of paper 25 on the bottom plate 31 makes contact with a height regulating member 33.

A half-moon roller 34 is disposed above the front end side of the bottom plate 31 and is axially supported, and is driven so as to rotate in the counter-clockwise direction around a shaft 35. An auxiliary roller 36 is additionally provided at one end of the half-circumferential face of the half-moon roller 34.

When the half-moon roller 34 is driven so as to rotate in the counter-clockwise direction, first the auxiliary roller 36 presses against the topmost sheet of paper 25 on the bottom plate 31, and while the auxiliary roller 36 rolls on the topmost sheet of paper 25, the paper batch on the bottom plate 31 is pushed downward against the spring restoring force, so that the topmost sheet of paper 25 is separated downward from the height regulating member 33. Next, the half-circumferential face of the half-moon roller 34 presses against the topmost sheet of paper 25, and the topmost sheet of paper 25 is pulled out by the half-circumferential face of the half-moon roller 34.

Similarly thereafter, each time that the half-moon roller 34 makes one rotation in the counter-clockwise direction, the topmost sheet of paper 25 is pushed away from the height regulating member 33 by the auxiliary roller 36, and the topmost sheet of paper 25 is pulled out by the half-circumferential face of the half-moon roller 34.

FIG. 3 is a cross-sectional view that shows an enlarged view of the vicinity of the half-moon roller 34. FIG. 4 is a cross-sectional view that shows a state in which the half-moon roller 34 has rotated approximately 90 degrees in the counter-clockwise direction. FIG. 5 is a cross-sectional view that shows a further enlarged view of the vicinity of one end of the half-moon roller 34 and the auxiliary roller 36.

The half-moon roller 34 as shown in FIGS. 3 to 5 includes a frame body 41 and a friction rubber 42. The frame body 41 is fixed to the shaft 35, and the friction rubber 42 is overlaid on the half-circumferential face of the frame body 41. Both ends 42a of the friction rubber 42 are fixed by hooking to respective engaging recesses 41a on both sides of the frame body 41. The outside surface of the friction rubber 42 serves as a half-circumferential face 34a of the half-moon roller 34, and part of the friction rubber 42 becomes one end 34b of the half-circumferential face 34a.

The rotatable auxiliary roller 36 is linked to an end 41b of the frame body 41 by an unshown linking structure, and the auxiliary roller 36 is disposed separated from the end 34b of the half-moon roller 34.

In FIG. 5, the half-circumferential face 34a of the half-moon roller 34, except for the one end 34b of the half-circumferential face 34a, traces a circular arc around the shaft 35 (shown in FIGS. 3 and 4). Also, an outermost circumferential position 36p of the auxiliary roller 36 is on a rotational trajectory S where the half-circumferential face 34a of the half-moon roller 34 rotates around the shaft 35, or in the vicinity of the rotational trajectory S.

Assuming that the one end 34b (part of the friction rubber 42) of the half-circumferential face 34a is a portion on the right side from a position 34p, the half-circumferential face 34a traces a circular arc around the shaft 35 on the left side from the position 34p, and the one end 34b of the half-circumferential face 34a is formed on the right side from the position 34p such that a curvature R of that circular arc gradually increases at positions closer to the auxiliary roller 36. Thus the one end 34b of the half-circumferential face 34a is formed so as to be enveloped to the inside.

When this sort of half-moon roller 34 is rotationally driven in the counter-clockwise direction together with the auxiliary roller 36, as previously described, the auxiliary roller 36 presses against a surface 25a of the topmost sheet of paper, and while the auxiliary roller 36 rolls on the surface 25a of the topmost sheet of paper, the paper batch on the bottom plate 31 is pushed downward against the spring restoring force.

At this time, the topmost sheet of paper is biased upward to always be pressed against the half-moon roller 34 or the auxiliary roller 36, so as shown in FIG. 6, the half-moon roller 34 and the auxiliary roller 36 are successively displaced relative to the surface 25a of the topmost sheet of paper. In FIG. 6, the solid line indicates a state in which only the auxiliary roller 36 is pressed against the surface 25a of the topmost sheet of paper, the dotted line indicates a state in which the one end 34b of the half-circumferential face 34a of the half-moon roller 34 and the auxiliary roller 36 are pressed against the surface 25a of the topmost sheet of paper, and the double-dotted chained line indicates a state in which only the half-circumferential face 34a of the half-moon roller 34 is pressed against the surface 25a of the topmost sheet of paper.

As is clear from FIG. 6, before the auxiliary roller 36 is separated from the surface 25a of the topmost sheet of paper, the one end 34b, which has a large curvature R, of the half-circumferential face 34a is pressed against the surface 25a of the topmost sheet of paper.

Then, the half-moon roller 34 further rotates so that the half-circumferential face 34a on the left side from the position 34p presses against the surface 25a of the topmost sheet of paper, and until the auxiliary roller 36 separates from the surface 25a of the topmost sheet of paper, the one end 34b, which has a large curvature R, of the half-circumferential face 34a continues to press against the surface 25a of the topmost sheet of paper.

Accordingly, for a predetermined period before the auxiliary roller 36 separates from the surface 25a of the topmost sheet of paper, the one end 34b, which has a large curvature R, of the half-circumferential face 34a continues to press against the surface 25a of the topmost sheet of paper.

While the one end 34b, which has a large curvature R, of the half-circumferential face 34a continues to press against the surface of the topmost sheet of paper, the auxiliary roller 36 also is pressing against the surface of the topmost sheet of paper, so the contact area of the half-circumferential face 34a and the auxiliary roller 36 with the surface of the topmost sheet of paper increases, and the spring restoring force that pushes up the paper batch on the bottom plate 31 is dispersed, and thus the contact force of the one end 34b of the half-circumferential face 34a against the surface of the topmost sheet of paper decreases. Therefore, the static frictional force between the topmost sheet of paper and the sheet of paper below the topmost sheet of paper decreases, so the topmost sheet of paper is easily pulled away from the sheet of paper below by the one end 34b of the half-circumferential face 34a, and thus conveyance of the topmost sheet of paper starts quickly. Immediately after the start of conveyance, only a smaller kinetic frictional force occurs between the topmost sheet of paper and the sheet of paper below the topmost sheet of paper, so pulling out of the topmost sheet of paper by the half-circumferential face 34a of the half-moon roller 34 is reliably continued. As a result, only the topmost sheet of paper is pulled out, and paper multi-feeding does not occur.

Above, a preferred embodiment of the invention was described with reference to the attached figures, but of course the invention is not limited by that example. It will be clear to a person having ordinary skill in the art that within the category described in the claims, various modified or revised examples can be arrived at, and it will be understood by a person having ordinary skill in the art that that such examples also are naturally encompassed by the technical scope of the invention.

For example, the extent to which the curvature R of the one end 34b of the half-moon roller 34 increases may be appropriately changed. Also, the invention is applicable not only to a paper feed tray that stores printing paper in a stacked manner, but also to an original tray that stores original paper in a stacked manner.

The present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all modifications or changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. A paper feed apparatus having a half-moon roller disposed above a plurality of sheets of paper stored in a stacked manner, and an auxiliary roller provided along one end of a half-circumferential face of the half-moon roller, the half-moon roller being rotated in a state in which a topmost sheet of paper has been put in contact with a height regulating member due to the sheets of paper being biased upward, so that the auxiliary roller and the half-circumferential face of the half-moon roller are successively pushed against the topmost sheet of paper, and while the sheets of paper are pushed down by the auxiliary roller or the half-circumferential face of the half-moon roller, the topmost sheet of paper is pulled out by the half-circumferential face of the half-moon roller:

the one end of the half-circumferential face of the half-moon roller being separated from the auxiliary roller, and a curvature of the one end of the half-circumferential face being gradually increased closer to the auxiliary roller.

2. The paper feed apparatus according to claim 1,

wherein before the auxiliary roller separates from the surface of the topmost sheet of paper, the one end of the half-circumferential face of the half-moon roller having a large curvature presses against the surface of the topmost sheet of paper.

3. The paper feed apparatus according to claim 1,

wherein the half-circumferential face of the half-moon roller comprises a frictional face.

4. The paper feed apparatus according to claim 1,

wherein the half-moon roller comprises a frame body that has been fixed to a shaft that serves as a rotational center of the half-moon roller, and a friction rubber that has been overlaid on the half-circumferential face of the frame body, the auxiliary roller being rotatably linked to one end of the frame body, and

the half-circumferential face of the half-moon roller is the outside surface of the friction rubber, and the one end of the half-circumferential face of the half-moon roller is part of the friction rubber.