Patent ID: 12208979

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

For the sake of simplicity, like reference numerals are given to identical or corresponding constituent elements such as parts and materials having the same functions, and redundant descriptions thereof are simplified or omitted unless otherwise required.

Initially with reference toFIG.1, a description is given of the overall configuration and operation of an image forming apparatus1according to an embodiment of the present disclosure.

FIG.1is a schematic view of the image forming apparatus1, which is a copier according to the present embodiment. In another embodiment of the present disclosure, the image forming apparatus1may be, for example, a printer, a facsimile machine, or a multifunction peripheral (MFP) having at least two of copying, printing, scanning, facsimile, and plotter functions.

InFIG.1, the image forming apparatus1includes a document reading device2, an exposure device3, an image forming device4, a transfer device7serving as an image forming unit, a document conveying device10, feeding devices12and13, a registration roller pair17serving as a conveyance roller pair, a fixing device20, and an output tray31. The document reading device2optically reads image data of a document D. The exposure device3irradiates a photoconductor5, which is included in the image forming device4, with exposure light L according to the image data read by the document reading device2. The image forming device4forms a toner image on the photoconductor5. The transfer device7transfers the toner image from the photoconductor5onto a sheet P.

The document conveying device10is an automatic document feeder (ADF) that conveys the document D placed on the document conveying device10to the document reading device2. Each of the feeding devices12and13feeds the sheet P accommodated in the corresponding input tray.

The registration roller pair17conveys the sheet P toward the transfer device7. The fixing device7includes a fixing roller21and a pressure roller22to fix the toner image borne as an unfixed image on the sheet P. The sheet P is ejected from a body of the image forming apparatus1onto the output tray31.

Each of the feeding devices12and13includes a vertically movable receptacle105and a sheet feeding assembly50serving as a sheet feeder.

With continued reference toFIG.1, a description is now given of a typical image forming operation of the image forming apparatus1.

Firstly, multiple rollers of the document conveying device10convey or feed the document D from a document tray in a direction indicated by arrow inFIG.1. The document D thus conveyed passes over the document reading device2. At this time, the document reading device2optically reads image data of the document D passing over the document reading device2.

The image data optically read by the document reading device2is converted into electrical signals. The electrical signals are transmitted to the exposure device3serving as a writer. The exposure device3then emits the exposure light L such as laser light according to the electrical signals (i.e., the image data) toward the surface of the photoconductor5of the image forming device4.

While the photoconductor5rotates clockwise inFIG.1, the image forming device4performs a given series of image forming processes, such as a charging process, an exposing process, and a developing process, to form a toner image corresponding to the image data on the photoconductor5.

Thereafter, the transfer device7serving as an image forming unit transfers the toner image from the surface of the photoconductor5onto the sheet P conveyed by the registration roller pair17.

Now, a description is given of how the sheet P is conveyed to the transfer device7serving as an image forming unit.

One of the feeding devices12and13disposed inside the body of the image forming apparatus1is selected automatically or manually. For example, the lower feeding device13is selected. Then, the sheet feeding assembly50feeds the uppermost sheet P of the sheets P accommodated in the feeding device13toward a conveyance passage K. The sheet P thus fed passes through the conveyance passage K along which multiple sheet conveyance rollers are disposed and reaches the position where the registration roller pair17is located. When the sheet P reaches the registration roller pair17, the rotation of the registration roller pair17has been stopped. As a leading end of the sheet P contacts an area of contact between the rollers of the registration roller pair17, the skew of the sheet P is corrected.

The activation of rotation of the registration roller pair17is timed to convey the sheet P of which the skew is corrected toward the transfer device7serving as an image forming unit such that the sheet P meets the image formed on the photoconductor5at an area of contact between the photoconductor5and the transfer device7.

After the transfer device7transfers the toner image from the photoconductor5onto the sheet P in the transfer process, the sheet P passing between the photoconductor5and the transfer device7reaches the fixing device20through the conveyance passage K. In the fixing device20, the sheet P is heated by the fixing roller21and pressed by the fixing roller21and the pressure roller22while the sheet P is conveyed through an area of contact, which may be referred to as a fixing nip, between the fixing roller21and the pressure roller22. Thus, the fixing device20fixes the toner image onto the sheet P at the fixing nip in the fixing process. After the sheet P bearing the toner image fixed in the fixing process is conveyed out from the fixing nip between the fixing roller21and the pressure roller22, the sheet P is output from the body of the image forming apparatus1onto the output tray31as an output image.

Thus, a series of image forming processes is completed.

Referring now toFIGS.2and3, a detailed description is given of the feeding devices12and13according to the present embodiment.

As an example, a description is now given of the lower feeding device13of the feeding devices12and13disposed in the body of the image forming apparatus1. Although the feeding devices12and13are disposed at different locations, the feeding devices12and13have like configurations. For this reason, a redundant description of the configuration of the upper feeding device12is herein omitted unless otherwise required.

Referring toFIGS.2and3, the feeding device13includes the receptacle105as a bottom plate, a sheet feeding assembly50, a pair of side fences101and102, an end fence103, a reference fence107, and a spring106serving as an elastic member. The receptacle105can hold a stack of sheets P, which may be referred to as a sheet bundle PT. The feeding assembly50feeds the sheet P placed on the receptacle105.

The receptacle105is movable up and down such that a downstream side (right side inFIG.2) in a feeding direction of the uppermost sheet P of the sheets P placed on the receptacle105reaches a given height position, which is a position where the uppermost sheet P contacts a pickup roller51. Note that the feeding direction of the sheet P is a direction in which the sheet P is fed and may be referred simply as the feeding direction in the following description.

Specifically, the receptacle105is supported so as to be pivotable about a pivot105ainside the feeding device13. The receptacle105is pivoted in forward and reverse directions about the pivot105athat is located at an upstream end of the receptacle105in the feeding direction. Thus, the receptacle105moves up and down.

Referring toFIG.2, the sheet feeding assembly50includes, for example, a feed roller52, the pickup roller51serving as a conveyor, and a separation roller53.

The feed roller52is close to and downstream from a leading end of the sheets P placed on the receptacle105in the feeding direction indicated by thick arrow inFIG.2. The feed roller52rotates counterclockwise inFIG.2along the feeding direction of the sheet P in contact with an upper face of the uppermost sheet P to feed the sheet P, together with the pickup roller51, in the feeding direction indicated by dash-dot arrow inFIG.2.

The pickup roller51as a conveyor rotates counterclockwise inFIG.2along the feeding direction in contact with the surface (i.e., the upper face) of the uppermost sheet P of the sheets P placed on the receptacle105to convey the uppermost sheet P toward the position of the feed roller52.

The separation roller53is disposed to form an area of contact, which may be referred to as a nip, between the separation roller53and the feed roller52. The separation roller53rotates in the forward direction, which is the clockwise direction indicated by dashed arrow inFIG.2, along the feeding direction when one sheet P is sandwiched at the nip or when no sheet P is sandwiched at the nip. By contrast, when a plurality of sheets P is sandwiched at the nip, the separation roller53rotates in a direction opposite to the above-described forward direction. In other words, the separation roller53rotates in the counterclockwise direction indicated by solid arrow inFIG.2. As a result, the uppermost sheet P of the plurality of sheets P sandwiched at the nip is fed in the feeding direction along the rotation of the feed roller52while the lower sheet or sheets P of the plurality of sheets P are conveyed in the direction opposite to the feeding direction (i.e., the forward direction). Thus, the multiple feeding of the sheets P is prevented.

The feeding device13according to the present embodiment includes the spring106, which is a compression spring, as an elastic member that biases the receptacle105to press the uppermost sheet P of a stack of sheets P on the receptacle105against the pickup roller51serving as a conveyor.

Specifically, the spring106serving as an elastic member lifts up the receptacle105that is pivotable about the pivot105ato press the uppermost sheet P of the stack of sheets P on the receptacle105against the pickup roller51that is secured at the given height position.

Such a configuration of the spring106moves up and down the receptacle105in the vertical direction, depending on a height H of the stack of sheets P (sheet bundle PT) on the receptacle105or the number of sheets P on the receptacle105, so that the uppermost sheet P of the stack of sheets P on the receptacle105contacts the pickup roller51. The pickup roller51feeds the uppermost sheet P of the sheets P on the receptacle105in the given feeding direction indicated by thick arrow inFIGS.2and3.

In the present embodiment, the compression spring106is used as an elastic member that biases the receptacle105upward. However, the elastic member is not limited to the compression spring106. Alternatively, the elastic member may be, for example, a tension spring, a torsion coil spring, or a plate spring. In the present embodiment, the receptacle105is directly biased by the elastic member (i.e., the spring106). Alternatively, the receptacle105may be indirectly biased by the elastic member via another member.

In the present embodiment, the pickup roller51is secured at the given height position. Alternatively, the pickup roller51may be movable between the given height position (i.e., the position where the pickup roller51contacts the uppermost sheet P of the sheets P on the receptacle105) and a retracted position where the pickup roller51is retracted upward from the given height position.

As illustrated inFIG.3, the feeding device13according to the present embodiment includes the pair of side fences101and102that regulates the position of the sheet P placed on the receptacle105in a width direction of the sheet P, which is a direction perpendicular to the surface of the paper on whichFIG.2is drawn and the vertical direction inFIG.3. The side fences101and102are disposed at opposed widthwise ends of the sheet P so as to sandwich the sheet P. The side fences101and102can be moved by a manual moving assembly in conjunction with each other in the width direction of the sheet P so as to conform to the widthwise size of the sheet P. In short, the interval between the side fences101and102in the width direction of the sheet P can be increased or decreased.

The feeding device13according to the present embodiment further includes the reference fence107and the end fence103that regulate the position of the sheet P placed on the receptacle105in the feeding direction, which is the lateral direction inFIGS.2and3. The reference fence107is disposed such that a downstream side face of the sheet P in the feeding direction (i.e., the leading end of the sheet P in the feeding direction) abuts against the reference fence107. The end fence103is disposed to contact an upstream side face of the sheet P in the feeding direction (i.e., the trailing end of the sheet P in the feeding direction). The end fence103can be moved by the manual moving assembly in the feeding direction so as to conform to the size of the sheet P in the feeding direction.

In the feeding device13according to the present embodiment, the spring106serving as an elastic member stops biasing the receptacle105in conjunction with the receptacle105, serving as an input tray that can hold a stack of sheets P, being pulled out from the body of the image forming apparatus1. Such a configuration facilitates replenishment of the sheets P (sheet bundle PT) on the lowered empty receptacle105while the receptacle105serving as an input tray is pulled out from the body of the image forming apparatus1. The spring106serving as an elastic member biases the receptacle105in conjunction with the attachment of the receptacle105serving as an input tray on which the sheets P (sheet bundle PT) are placed into the body of the image forming apparatus1.

As illustrated inFIG.2, the pickup roller51starts to rotate counterclockwise in contact with the upper face of the uppermost sheet P of the sheets P placed on the receptacle105. At the same time, the feed roller52and the separation roller53start to rotate. As a result, the pickup roller51conveys the uppermost sheet P or upper sheets P of the sheet bundle PT placed on the receptacle105toward the nip between the feed roller52and the separation roller53. At the nip, one sheet P is separated from other sheets P and conveyed toward the image forming unit by the feed roller52(and the pickup roller51).

Referring now toFIGS.2to7, a detailed description is given of a configuration and operation of the feeding device13of the image forming apparatus1according to the present embodiment.

As described above with reference toFIGS.2and3, the feeding device13includes the receptacle105, the pickup roller51serving as a conveyor, the spring106serving as an elastic member, and the pair of side fences101and102.

The receptacle105as a bottom plate is movable up and down. A plurality of sheets P (sheet bundle PT) can be stacked on the receptacle105. In other words, the receptacle105is vertically movable and can hold a stack of sheets P.

The pickup roller51functions as a conveyor that feeds the uppermost sheet P of the stack of sheets P on the receptacle105in the given feeding direction indicated by thick arrow inFIGS.2to4C.

The spring106is an elastic member that biases the receptacle105to press the uppermost sheet P of the stack of sheets P on the receptacle105against the pickup roller51serving as a conveyor. The force that presses the sheet P against the pickup roller51as described above may be referred to as “feeding pressure (pickup pressure).”

As illustrated inFIGS.3and5, the side fences101and102as a pair of fences include fence faces101aand102a, respectively. The fence faces101aand102acan contact side end faces of the stack of sheets P on the receptacle105.

Referring toFIGS.3to5, the feeding device13according to the present embodiment includes a brush110, which is a brush-like member serving as a load adjuster.

At least when the height H of the stack of sheets P on the receptacle105is equal to or greater than a given value Hx, which is a value slightly smaller than a height H2of the stack of sheets P described later with reference toFIG.4B, the brush110functions as a load adjuster that reduces the magnitude of load applied downward, in a direction in which the feeding pressure is reduced, to the stack of sheets P on the receptacle105, in response to a decrease in the height H.

In other words, at least when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx, the brush110serving as a load adjuster gradually reduces the feeding pressure (pickup pressure) along with a gradual decrease in the height H due to a decrease in the number of sheets P as the sheets P are fed.

In the present description, the load adjuster (i.e., the brush110) may be referred to as a load applier that applies a load to reduce the force that presses the uppermost sheet P against the conveyor (i.e., the pickup roller51) when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx. In the present embodiment, the brush110serving as the load applier changes the load to the stack of sheets P on the receptacle105, depending on the height H of the stack of sheets P on the receptacle105.

Thus, the brush110allows the feeding device13to stably feed the sheets P when the decrease in the height H or the number of sheets P stacked on the receptacle105along with the feeding of the sheets P reduces the feeding pressure (pickup pressure) applied to the pickup roller51from the uppermost sheet P of the sheets P on the receptacle105biased by the spring106serving as an elastic member.

Specifically, when the feeding pressure (pickup pressure) is excessively high, the sheets P may be fed at the same time due to an increased adhesion force caused by the friction between the sheets P. By contrast, when the feeding pressure (pickup pressure) is excessively low, the sheets P may fail to be fed due to an insufficient conveying force for feeding or conveying the sheet P.

Referring toFIGS.6and7, in the present embodiment, an appropriate range of the feeding pressure (pickup pressure) that causes neither the multiple feeding nor non-feeding of the sheets P is from 1.5 N to 9 N.

The feeding pressure (pickup pressure) is generally obtained by subtracting the weight of the sheets P on the receptacle105and the weight of the receptacle105from the spring force of the spring106corresponding to the height H of the stack of sheets P on the receptacle105. In the following description, the height H of the stack of sheets P on the receptacle105may be referred to simply as a sheet height H.

In short, referring toFIGS.4A to4CandFIG.7, the feeding pressure (pickup pressure) decreases as the sheet height H decreases.

When smaller sheets P are stacked at the sheet height H, the feeding pressure (pickup pressure) increases because the smaller sheets P has a smaller weight. Specifically, referring to Q1and Q2(or R1and R2) in the graph ofFIG.7, when the sheets P of the A6 size (small size) are stacked on the receptacle105, the percentage of change (gradient) of the feeding pressure indicated by the vertical axis with respect to the sheet height H indicated by the horizontal axis is greater than that when the sheets P of the A3 size (large size) are stacked on the receptacle105.

To keep a given appropriate range, which is a range of 1.5 N to 9 N in the present embodiment, of the feeding pressure that changes depending on the sheet height H and the sheet size, it is insufficient to simply adjust the spring force of the spring106serving as an elastic member or uniformly apply the load for reducing the spring force to the receptacle105with, for example, a brush-like inclination restraint, regardless of changes in the sheet height H. For example, in a case where the spring force of the spring106is simply adjusted in the feeding device13having a relationship between the sheet height H (horizontal axis) and the feeding pressure (vertical axis) as indicated by Q1and Q2inFIG.7to prevent Q1(A6 size) from being in a multiple-feeding area where the multiple feeding occurs, to set the feeding device13so as to have a relationship between the sheet height H (horizontal axis) and the feeding pressure (vertical axis) as indicated by R1and R2inFIG.7, R1(A6 size) and R2(A3 size) are partially in a non-feeding area where non-feeding occurs at a relatively small height H.

As described above, in a typical feeding device, as the feeding operation proceeds and changes (reduces) the height of a stack of sheets or the number of sheets stacked on a receptacle, a feeding pressure as a force that presses, against a conveyor, the uppermost sheet of the stack of sheets on the receptacle biased by an elastic member may deviate from an appropriate range. Such an unstable feeding pressure destabilizes the sheet feeding performed by a feeding device.

By contrast, in the present embodiment, as indicated by S1and S2in the graph ofFIG.6, the brush110serving as a load adjuster reduces the feeding pressure (pickup pressure) as the height H gradually decreases at least when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx, which is about 20 mm in the present embodiment. Accordingly, regardless of the sheet size or changes in the sheet height H, the feeding pressure (pickup pressure) falls within a range (of 1.5 N to 9 N in the present embodiment) that causes neither the multiple feeding nor non-feeding of the sheets P.

In particular, in the present embodiment, the brush110serving as a load adjuster applies a reduced magnitude of load downward to the stack of sheets P on the receptacle105in response to the decrease in the height H, when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx, which is about 20 mm in the present embodiment.

By contrast, when the height H of the stack of sheets P on the receptacle105is less than the given value Hx, which is about 20 mm in the present embodiment, the brush110serving as a load adjuster applies no load to the stack of sheets P on the receptacle105.

Such a configuration increases the margin for the non-feeding when the height H is relatively small and easily allows the feeding pressure (pickup pressure) to fall within a range (of 1.5 N to 9 N in the present embodiment) that causes neither the multiple feeding nor non-feeding of the sheets P, regardless of the sheet height H or the sheet size.

More specifically, referring toFIGS.3and5, the brush110as a load adjuster is disposed on each of the fence face101aof the side fence101and the fence face102aof the side fence102.

Since the load of the brush110is applied to the stack of sheets P on the receptacle105from the opposed widthwise ends of the stack of sheets P in a well-balanced manner, the pickup roller51stably feeds the sheets P.

Referring toFIG.5, the brush110is disposed such that bristles110bof the brush110are inclined downward, in a direction opposite to a direction in which the receptacle105moves up.

Specifically, in the present embodiment, the brush110has a substantially rectangular shape and is substantially equivalent to a lint brush. The brush110includes the flocked or napped bristles110bmade of, for example, nylon. The bristles110bare uniformly inclined in a given direction, which may be referred to as a falling direction in the following direction.

As described above, since the bristles110bare inclined downward, the downward load of the brush110is easily applied to the stack of sheets P on the receptacle105.

The length of the bristles110bof the brush110is adjusted by thermal fusion cutting to reduce the collapse of the bristles110b.

Referring toFIGS.3to4C, the brush110is disposed on or attached, via a double-sided adhesive tape, to an upper portion (specifically, a part of the upper portion) of each of the fence faces101aand102aupstream from the pickup roller51in the feeding direction, as illustrated to the left of the pickup roller51inFIGS.3to4C.

Referring toFIGS.4A to4C, the receptacle105is pivoted about the pivot105athat is located upstream from the brush110in the feeding direction, to move up and down.

In such a configuration, as the sheet feeding is repeated and the height H or the number of sheets P stacked on the receptacle105decreases, the pivot angle or inclined angle of the receptacle105about the pivot105aincreases.

At least when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx, the brush110contacts the stack of sheets P on the receptacle105in a decreased width X along the feeding direction in response to the decrease in the height H. Note that the width X along the feeding direction is a contact width along a direction along an inclined placement face of the receptacle105.

Specifically, in the present embodiment, when the sheet height H is equal to or greater than the given value Hx and is a sufficiently large sheet height H1as illustrated inFIG.4A, a contact width X1, which is a width along the feeding direction in which the stack of sheets P contacts the brush110, is greater than a contact width X2when the sheet height H is the sheet height H2, which is smaller than the sheet height H1, as illustrated inFIG.4B. In other words, in a case where the sheet height H is equal to or greater than the given value Hx, the load (i.e., the force for reducing the feeding pressure) of the brush110on the stack of sheets P on the receptacle105decreases as the sheet height H decreases.

By contrast, when the sheet height H is less than the given value Hx and is a sufficiently small sheet height H3as illustrated inFIG.4C, the sheet P does not contact the brush110. In short, the contact width X is 0.

Accordingly, regardless of the sheet height H or the sheet size, the feeding pressure (pickup pressure) falls within a range that causes neither the multiple feeding nor non-feeding of the sheets P.

Preferably, the vertical interval between the adjacent bristles110bof the brush110is shorter than the thickness (for example, the basis weight of about 52 g/m2) of a thinnest sheet P that can be fed. In other words, the brush110includes the adjacent bristles110bat a vertical interval shorter than the thickness of a thinnest sheet P feedable.

Such a configuration allows the bristles110bof the brush110to enter between the sheets P stacked on the receptacle105and allows the brush110to easily exert the load (i.e., the force for reducing the feeding pressure).

Now, a detailed description is given of the function of the brush110serving as a load adjuster.

In the present embodiment, the pressure reduction, which is a reduction of the feeding pressure), performed by the brush110as a load adjuster is proportional to the pressing force (i.e., the spring force of the spring106) for lifting the sheets P on the receptacle105and the contact width X in which the sheet P and the brush110contact each other.

When the sheet height H is the sufficiently large sheet height H1as illustrated inFIG.4A, the contact width X1in which the sheet P and the brush110contact each other is substantially equal to the width of the brush110. As the sheet height H gradually decreases to the sheet height H2, the contact width X in which the sheet P and the brush110contact each other also decreases to the contact width X2as illustrated inFIG.4B. As the sheet height H further gradually decreases, the contact width X also gradually decreases and eventually becomes 0 as illustrated inFIG.4C. Specifically, S1and S2in the graph ofFIG.6indicate a greater decrease in the feeding pressure (pickup pressure) as the height H increases and a smaller decrease in the feeding pressure (pickup pressure) as the height H decreases, from Q1and Q2, respectively, which indicate a relationship between the feeding pressure (pickup pressure) and the sheet height H in a case where the brush110is not disposed. When the height H is less than the given value Hx, the feeding pressure (pickup pressure) is not below Q1or Q2, as indicated by S1and S2overlapping Q1and Q2, respectively, in the graph ofFIG.6.

In short, the multiple feeding of the sheets P does not occur even when the height H is relatively large whereas the non-feeding of the sheets P does not occur even when the height H is relatively small. Thus, the excellent feeding performance is maintained.

Referring now toFIGS.8A and8B, a description is given of some modifications of the embodiment described above.

As illustrated inFIGS.8A and8B, in the feeding devices13according to the modifications, the receptacle105moves up and down while keeping the placement face substantially horizontal, instead of being pivoted about the pivot105a.

Like the embodiment described above, according to the modifications illustrated inFIGS.8A and8B, the side fences101and102are disposed as fences including the fence faces101aand102a, respectively, which can contact the end faces of the stack of sheets P (sheet bundle PT) on the receptacle105. The brush110serving as a load adjuster is disposed on each of the fence faces101aand102a.

The brush110illustrated inFIG.8Ais substantially a triangle having an upper horizontal width (i.e., the upper width X along the lateral direction inFIG.8A) smaller than a lower horizontal width (i.e., the lower width X along the lateral direction inFIG.8A).

On the other hand, in the brush110illustrated inFIG.8B, the stiffness of the bristles110blocated above is smaller than the stiffness of the bristles110blocated below. In other words, the brush110illustrated inFIG.8Bincludes the upper bristles110bhaving a stiffness smaller than the stiffness of the lower bristles110b. Specifically, such a difference in the stiffness of the bristles110bmay be caused by changing, for example, the thickness, length, or material of the bristles110b, or a combination thereof. More specifically, for example, the thickness of the bristles110bmay be gradually increased downward. The length of the bristles110bmay be gradually increased downward. The material of the bristles110bmay be changed for each vertical positions to gradually increase the stiffness of the bristles110bdownward.

Like the feeding device13according to the embodiment described above, each of the feeding devices13according to the modifications illustrated inFIGS.8A and8Bapplies, with the brush110serving as a load adjuster, a reduced magnitude of load downward to the stack of sheets P on the receptacle105in response to the decrease in the height H, at least when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx.

Accordingly, the feeding pressure (pickup pressure) from the uppermost sheet P of the stack of sheets P on the receptacle105against the pickup roller51is less likely to deviate from the appropriate range in response to changes in the height H of the stack of sheets P on the receptacle105.

Although the side fences101and102are used as the fences on each of which the brush110is disposed in the present modifications, the reference fence107or the end fence103may be used as the fence on which the brush110is disposed.

As described above, the feeding device13according to the present embodiment includes the receptacle105that is vertically movable and can hold a stack of sheets P, the pickup roller51serving as a conveyor that feeds the uppermost sheet P of the stack of sheets P on the receptacle105in the given feeding direction in which a sheet of the stack of sheets P is fed, and the spring106serving as an elastic member that biases the receptacle105to press the uppermost sheet P of the stack of sheets P on the receptacle105against the pickup roller51. The feeding device13according to the present embodiment further includes the brush110serving as a load adjuster that applies a reduced magnitude of load downward to the stack of sheets P on the receptacle105in response to the decrease in the height H, at least when the height H of the stack of sheets P on the receptacle105is equal to or greater than the given value Hx.

Accordingly, the feeding device13according to the present embodiment optimizes the feeding pressure (pickup pressure) from the uppermost sheet P of the stack of sheets P on the receptacle105against the pickup roller51, in response to changes in the height H of the stack of sheets P on the receptacle105.

Although the feeding device13is disposed in the image forming apparatus1that is a monochrome image forming apparatus in the present embodiment, the feeding device13may be disposed in a color image forming apparatus in another embodiment of the present disclosure.

Although the feeding device13is disposed in the image forming apparatus1that is an electrophotographic image forming apparatus in the present embodiment, the feeding device13may be disposed in another type of image forming apparatus such as an inkjet image forming apparatus or a stencil printer in another embodiment of the present disclosure.

Although the feeding device13is disposed inside the image forming apparatus1in the present embodiment, the feeding device13may be used as a feeding device that is exposed to the outside of the image forming apparatus1, such as a bypass feeding device in another embodiment of the present disclosure. In still another embodiment of the present disclosure, the feeding device13may be used as a feeding device that feeds or conveys the document D in the document conveying device10as an ADF.

Any of the cases described above exhibits substantially the same advantages as the advantages of the present embodiment.

Although the entire receptacle105is vertically movable (pivotable) in the present embodiment, only a part of the receptacle105(specifically, a downstream portion of the receptacle105in the feeding direction) may be vertically movable (pivotable) in another embodiment of the present disclosure.

Although the pickup roller51serving as a roller is used as a conveyor in the present embodiment, the conveyor is not limited to the pickup roller51. For example, a conveyance belt serving as a belt may be used as the conveyor in another embodiment of the present disclosure.

Although the brush110is used as a load adjuster in the present embodiment, the load adjuster is not limited to the brush110provided that the load adjuster can apply a load downward to the stack of sheets P on the receptacle105. For example, the load adjuster may be a film-like member having a relatively high coefficient of friction or a member having a surface with jagged irregularities in another embodiment of the present disclosure. The load adjuster may be a part of the fence face of the fence in one or some embodiments of the present disclosure.

In the present embodiment, the load adjuster reduces the load in response to the decrease in the height H when the sheet height H is equal to or greater than the given value Hx and applies no load when the sheet height H is less than the given value Hx. In a case where a sufficient feeding performance is ensured when the sheet height H is less than the given value Hx, the load adjuster may reduce the load in response to the decrease in the height H.

Any of the cases described above exhibits substantially the same advantages as the advantages of the present embodiment.

In the present description, the sheet P is defined as any sheet-like recording medium, such as general paper, coated paper, label paper, or overhead projector (OHP) transparency.

According to one aspect of the present disclosure, a feeding device is provided that optimizes a feeding pressure from a sheet on a receptacle against a conveyor, in response to changes in the height of a stack of sheets on the receptacle. Also provided is an image forming apparatus incorporating the feeding device.

The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.