Sheet cassette, feeder, and image forming apparatus

A sheet cassette (1) includes a first sheet accommodation section (3), a second sheet accommodation section (5), and a restricting section (7). The restricting section (7) includes a lever section (70), a first engagement section (38a), and a second engagement section (78a). The lever section (70) is shiftable between a first engaged position, a second engaged position, and a disengaged position. The first engaged position is a position where a distal end portion (76) protrudes from a sheet loading surface (F2) of a second bottom (50) with no sheets loaded on the second bottom (50), and the first engagement section (38a) and the second engagement section (78a) are in engagement. The second engaged position is a position where the distal end portion (76) is pushed down out of the first engaged position in accordance with the number of sheets loaded on the second bottom (50), and the first engagement section (38a) and the second engagement section (78a) are in engagement. The disengaged position is a position where the engagement between the first engagement section (38a) and the second engagement section (78a) is released. Strength of the engagement between the first engagement section (38a) and the second engagement section (78a) is larger when the lever section (70) is in the second engaged position than when the lever section (70) is in the first engaged position.

TECHNICAL FIELD

The present invention relates to a sheet cassette in which a plurality of sheets are loaded, a feeder, and an image forming apparatus.

BACKGROUND ART

A sheet feed cassette disclosed in Patent Literature 1 includes a cassette main body and a cassette extendable section. The size of the sheet feed cassette is adjusted by sliding in and out the cassette extendable section according to the size of sheets.

The sheet feed cassette includes a lock mechanism. The lock mechanism includes an engagement hole and a lock button. The engagement hole is provided in the cassette main body. The lock button is provided in the cassette extendable section.

The lock button is in engagement with the engagement hole in a locked state. Pushing down the lock button releases the lock button from the engagement hole. Thus, the locked state of the cassette main body and the cassette extendable section is released. As a result, the cassette extendable section becomes slidable relative to the cassette main body.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, the sheet feed cassette disclosed in Patent Literature 1 has the following problem. That is, since manipulating the lock button itself does not slide the cassette extendable section, a user is required to grab a certain part of the cassette extendable section and slide in or out the cassette extendable portion. Accordingly, manipulation of at least two parts is needed in order to release the locked state and slide in or out the cassette extendable section. Furthermore, once sheets are loaded, the locked state of the cassette main body (main cassette) and the cassette extendable section (sliding cassette) is generally required to be hard to release.

In view of the above-described problem, the present invention has been made to provide: a sheet cassette whose size is adjustable by simple manipulation and which is capable of restricting release of a locked state of a main cassette and a sliding cassette after loading of sheets; a feeder; and an image forming apparatus.

Solution to Problem

According to a first aspect of the present invention, a sheet cassette is to be loaded with a plurality of sheets and is adjustable in size. The sheet cassette includes a first sheet accommodation section, a second sheet accommodation section, and a restricting section. The first sheet accommodation section has a first bottom on which the plurality of sheets are loaded. The second sheet accommodation section has a second bottom on which the plurality of sheets are loaded. The second sheet accommodation section is attached to the first sheet accommodation section so as to be slidable between a retracted position where the second sheet accommodation section is retracted in the first sheet accommodation section and an extended position where the second sheet accommodation section is drawn out from the first sheet accommodation section in an extending direction. The restricting section restricts sliding of the second sheet accommodation section in the retracted position. The restricting section includes a lever section, a first engagement section, and a second engagement section. The lever section extends from the second bottom in the extending direction and has a distal end portion in the extending direction that is swingable in upward and downward directions. The first engagement section is disposed in the first bottom. The second engagement section is disposed in the lever section and is engageable with the first engagement section. The lever section is shiftable between a first engaged position, a second engaged position, and a disengaged position while the second sheet accommodation section is in the retracted position. The first engaged position is a position where no sheets are loaded on the second bottom, the distal end portion protrudes from a sheet loading surface of the second bottom, and the first engagement section and the second engagement section are in engagement. The second engaged position is a position where the distal end portion is pushed down out of the first engaged position in accordance with a number of sheets loaded on the second bottom, and the first engagement section and the second engagement section are in engagement. The disengaged position is a position where the lever section is lifted out of the first engaged position, and thus the engagement between the first engagement section and the second engagement section is released. Strength of the engagement between the first engagement section and the second engagement section is larger when the lever section is in the first engaged position than when the lever section is in the second engaged position.

According to a second aspect of the present invention, a feeder includes the sheet cassette according to the first aspect and a feeding section. The feeding section feeds a sheet from the sheets in the sheet cassette.

According to a third aspect of the present invention, an image forming apparatus includes the feeder according to the second aspect and an image forming section. The image forming section forms an image on the sheet fed by the feeder.

Advantageous Effects of Invention

According to the present invention, a user can slide the second sheet accommodation section by lifting the lever section to release the engagement, and subsequently pulling the lever section in a direction away from the first sheet accommodation section or pushing the lever section in a direction toward the first sheet accommodation section. That is, the releasing of the engagement and the sliding can be performed by a series of manipulation actions on the lever section. Once sheets are loaded, the distal end portion of the lever section is pushed down and the lever section is shifted from the first engaged position to the second engaged position. As a result, strength of the engagement between the first engagement section and the second engagement section is increased. It is therefore possible to adjust the size of the sheet cassette by simple manipulation and restrict release of a locked state of the main cassette and the sliding cassette after loading of sheets.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that elements in the drawings that are the same or equivalent are labelled using the same reference signs and description thereof is not repeated.

First Embodiment

Basic Principle

The basic principle of a sheet cassette1according to the first embodiment of the present invention will be described with reference toFIGS. 1 to 6.FIG. 1is a perspective view of the sheet cassette1. A plurality of sheets (not shown) are loaded in the sheet cassette1which is adjustable in size. The sheet cassette1includes a main cassette3(first sheet accommodation section), a sliding cassette5(second sheet accommodation section), and a first restricting section7(restriction section). The main cassette3has a bottom member30(first bottom) on which a plurality of sheets are loaded. The bottom member30has a sheet loading surface F1.

The sliding cassette5has a bottom member50(second bottom) on which a plurality of sheets are loaded. The bottom member50has a sheet loading surface F2. The sliding cassette5is slidably attached to the main cassette3. More specifically, the sliding cassette5is attached to the main cassette3so as to be slidable between a retracted position where the sliding cassette5is retracted in the main cassette3and an extended position where the sliding cassette5is drawn out from the main cassette3in a direction A1away from the main cassette3(hereinafter, referred to as an “extending direction A1”). InFIG. 1, the sliding cassette5is in the retracted position. The restricting section7restricts sliding of the sliding cassette5in the retracted position.

FIG. 2is an enlarged perspective view of the first restricting section7of the sheet cassette1.FIG. 3is a cross-sectional view illustrating an engaged state of the first restricting section7, taken along line III-III inFIG. 2(first engaged position). InFIG. 3, the sliding cassette5is in the retracted position. Furthermore, inFIG. 3, no sheets are loaded in the sheet cassette1, and no external force is exerted on a projected portion76.FIG. 4is a cross-sectional view illustrating a disengaged state of the first restricting section7(disengaged position).

The first restricting section7includes an engagement pawl38a(first engagement section), a lever section70, and a mating engagement pawl78a(second engagement section). The engagement pawl38ais disposed in the bottom member30of the main cassette3. The lever section70is disposed in the bottom member50of the sliding cassette5. The lever section70extends from the bottom member50in the extending direction A1. The mating engagement pawl78ais disposed in the lever section70and is engageable with the engagement pawl38a. The engagement between the engagement pawl38aand the mating engagement pawl78acan be released by lifting the lever section70.

The lever section70includes a proximal end portion72, a lower portion75, and the projected portion76(distal end portion). The proximal end portion72is connected with the bottom member50. The lever section70starts from the proximal end portion72and extends in the extending direction A1. The lower portion75is formed continuous from the proximal end portion72and disposed lower than the sheet loading surface F2of the bottom member50. The projected portion76is the distal end portion of the lever section70in the extending direction A1. The projected portion76is formed continuous from the lower portion75and projected upward from the sheet loading surface F2. The proximal end portion72is elastic, and thus the projected portion76is swingable in upward and downward directions (in an upward direction B1or in a downward direction B2).

The lever section70is shiftable from the first engaged position (FIG. 3) to the disengaged position (FIG. 4) when so manipulated. A second engaged position will be described later. As illustrated inFIG. 3, the first engaged position is a position where while the sliding cassette5is in the retracted position, no sheets are loaded on the bottom member50, the projected portion76protrudes from the sheet loading surface F2of the bottom member50, and the engagement pawl38aand the mating engagement pawl78aare in engagement. Posture of the lever section70while in the first engaged position may be referred to as a first posture. As illustrated inFIG. 4, the disengaged position is a position where while the sliding cassette5is in the retracted position, the lever section70is lifted out of the first engaged position, and thus the engagement between the engagement pawl38aand the mating engagement pawl78ais released. Posture of the lever section70while in the disengaged position may be referred to as a third posture.

Shift of the lever section70from the first engaged position to the disengaged position releases the engagement between the engagement pawl38aand the mating engagement pawl78a, and allows the lever section70to be pulled in the extending direction A1to slide the sliding cassette5and extend a size of the sheet cassette1. As a result, the sliding cassette5is slid from the retracted position to the extended position.

That is, when the sliding cassette5is in the retracted position, it is possible to slide out the sliding cassette5up to the extended position by pulling the lever portion70in the extending direction A1while the engagement between the engagement pawl38aand the mating engagement pawl78ais kept released by lifting the lever section70, that is, while the lever section70is in the disengaged position.

FIG. 5is a cross-sectional view illustrating a second restricting section21of the sheet cassette1, taken along line V-V going through an engagement hole41illustrated inFIG. 1. InFIG. 5, the sliding cassette5is in the extended position. As illustrated inFIGS. 1 and 5, the sheet cassette1further includes the second restricting section21. The second restricting section21restricts sliding of the sliding cassette5in the extended position.

The second restricting section21includes a pair of engagement holes41and a pair of engagement protrusions61. The engagement holes41are through holes formed in the bottom member50of the sliding cassette5. In the first embodiment, the engagement holes41are each rectangular and are formed in a region of the bottom member50that is closest to a forward end member32.

The engagement protrusions61are formed in the bottom member30of the main cassette3so that the engagement protrusions61mate with the engagement holes41when the sliding cassette5is in the extended position. In the first embodiment, the engagement protrusions61are each formed in a region of the bottom member30that is closer to a rearward end member52. The engagement protrusions61have a triangular cross-section and project from the sheet loading surface F1. The engagement protrusions61each have an engagement surface62and an inclined surface63. The inclined surface63is inclined upward in a contracting direction A2from the sheet loading surface F1. The contracting direction A2, which is opposite to the extending direction A1, is a direction in which the sliding cassette5moves toward the main cassette3.

As the sliding cassette5is drawn out in the extending direction A1into the extended position, each of the engagement protrusions61comes in engagement with the corresponding engagement hole41. Specifically, the engagement surface62of the engagement protrusion61comes in engagement with an engagement surface42forming the engagement hole41. As a result, sliding of the sliding cassette5in the extended position is restricted.

However, since the inclined surface63is inclined upward in the contracting direction A2, merely pushing in the sliding cassette5in the contracting direction A2can release the engagement (mating) between the engagement protrusions61and the engagement holes41, and bring the sliding cassette5into the retracted position. Therefore, no special engagement (mating) releasing mechanism is needed in order to shift the sliding cassette5from the extended position to the retracted position.

As described with reference toFIG. 4, a user shifts the lever section70from the first engaged position to the disengaged position to release the engagement, and subsequently pulls the lever section70in the extending direction A1or pushes the lever section70in the contracting direction A2to slide in or out the sliding cassette5. That is, the releasing of the engagement and the sliding can be performed by a series of manipulation actions on the lever section70. Consequently, the size of the sheet cassette1can be adjusted by simple manipulation.

FIG. 6illustrates the engaged state of the first restricting section7, during which the lever section70is in the second engaged position. InFIG. 6, a plurality of sheets P are loaded in the sheet cassette1. The second engaged position is a position where while the sliding cassette5is in the retracted position, the projected portion76is pushed down out of the first engaged position in accordance with the number of sheets P loaded on the bottom member50, and the engagement pawl38aand the mating engagement pawl78aare in engagement. Posture of the lever section70in the second engaged position may be referred to as a second posture. Strength of the engagement between the engagement pawl38aand the mating engagement pawl78ais larger when the lever section70is in the second engaged position than when the lever section70is in the first engaged position.FIG. 6illustrates a situation in which the projected portion76is retracted below the sheet loading surface F2and the engagement strength is at its maximum.

Since the lever section70is shifted from the first engaged position to the second engaged position by the projected portion76pushed down due to loading of the sheets P, the strength of the engagement between the engagement pawl38aand the mating engagement pawl78ais increased. As a result, the locked state of the main cassette3and the sliding cassette5can be prevented from being released after loading of the sheets P.

As described with reference toFIGS. 3, 4, and 6, the lever section70is shiftable between the first engaged position (FIG. 3), the second engaged position (FIG. 6), and the disengaged position (FIG. 4) while the sliding cassette5is in the retracted position.

[General Configuration of Sheet Cassette1]

General configuration of the sheet cassette1will be described with reference toFIG. 1. In the first embodiment, an X axis and a Y axis are horizontal axes perpendicular to one another, and a Z axis is a vertical axis. The extending direction A1and the contracting direction A2are substantially parallel to the X axis. A sheet conveyance direction in the sheet cassette1is substantially the same as the contracting direction A2, and a direction opposite to the sheet conveyance direction is substantially the same as the extending direction A1. In embodiments of the present invention, a “forward end” or a “forward end portion” of a member or section refers to a forward end or a forward end portion of the member or section in the contracting direction A2, that is, a forward end or a forward end portion of the member or section in the sheet conveyance direction. A “rearward end” or a “rearward end portion” of a member or section refers to a rearward end or a rearward end portion of the member or section in the contracting direction A2, that is, a rearward end or a rearward end portion of the member or section in the sheet conveyance direction. A positive direction of the Z axis is the upward direction B1, and a negative direction of the Z axis is the downward direction B2(seeFIG. 3).FIG. 1illustrates the sheet cassette1in a minimum size state with the sliding cassette5pushed in the contracting direction A2to the maximum.

The sliding cassette5is slidable in the extending direction A1relative to the main cassette3. Sliding the sliding cassette5in the extending direction A1therefore extends the size of the sheet cassette1, allowing larger-sized sheets P to be loaded in the sheet cassette1. The sliding cassette5is slidable also in the contracting direction A2relative to the main cassette3. Sliding the sliding cassette5in the contracting direction A2therefore contracts the size of the sheet cassette1, allowing smaller-sized sheets P to be loaded in the sheet cassette1. In the first embodiment, the sheet cassette1can be adjusted to a normal size with the sliding cassette5pushed in to the maximum and to an extended size with the sliding cassette5drawn out to the maximum. The extended size defines a maximum size of sheets P that can be loaded in the sheet cassette1.

The main cassette3is formed mainly from a synthetic resin. Examples of the synthetic resin include acrylonitrile butadiene styrene (ABS) resins. The main cassette3includes the plate-like bottom member30, a pair of side end members31, the forward end member32, a panel33, a lift plate35, a pair of shafts36, and a pair of side end guides34. The main cassette3is open at a rearward end thereof. The forward end member32is stood from the bottom member30and elongated along the Y axis. A sheet conveyance guide8and a retard roller6aare disposed in the forward end member32. The panel33is disposed on a front surface of the forward end member32. The pair of side end members31are opposite to one another, stood from the bottom member30, and elongated along the X axis.

The pair of shafts36are disposed corresponding to the pair of side end members31. The lift plate35is disposed on the sheet loading surface F1of the bottom member30. Each side of a proximal end portion of the lift plate35has a supporting hole (not shown) through which the corresponding one of the shafts36penetrates. Each end of the proximal end portion of the lift plate35is rotatably supported by the shaft36. Thus, a distal end portion of the lift plate35can be lifted up and down, rotating about the shafts36.

The pair of side end guides34are disposed opposite to one another and corresponding to the pair of side end members31. Each side end guide34is stood along the corresponding one of the side end members31. The pair of side end guides34are connected with a rack-and-pinion mechanism (not shown). Accordingly, the pair of side end guides34are geared to one another and movable in directions toward one another or in directions away from one another along the Y axis.

The sliding cassette5is formed manly from a synthetic resin (for example, an ABS resin). The sliding cassette5includes the first restricting section7, the plate-like bottom member50, a pair of side end members51, a rearward end member52, a rearward end guide53, a pair of rails54, and a plurality of ratchet teeth55. The first restricting section7is disposed in the bottom member50. The sliding cassette5is open at a forward end thereof. The pair of side end members31are opposite to one another, stood from the bottom member50, and elongated along the X axis. The rearward end member52is stood from the bottom member30and elongated along the Y axis.

The pair of rails54are formed on the bottom member50and elongated along the X axis. The plurality of ratchet teeth55are disposed between the pair of rails54, along the X axis. The rearward end guide53is stood along the rearward end member52. The rearward end guide53is movable along the rails54. Engagement pawls56are formed in a lower part of the rearward end guide53. The engagement pawls56can engage with the ratchet teeth55and disengage from the ratchet teeth55. Thus, the rearward end guide53can be fixed at any location along the rails54.

The sliding cassette5is attached to the main cassette3such that the bottom member50is disposed over the bottom member30in a region where the sliding cassette5overlaps the main cassette3. The sheets P are stacked on one another in the positive direction of the Z axis over the sheet loading surface F1of the bottom member30, an upper surface of the lift plate35, and the sheet loading surface F2of the bottom member50. More specifically, a forward end portion of the sheets P is placed over the sheet loading surface F1and the upper surface of the lift plate35, whereas a rearward end portion of the sheets P is placed over the sheet loading surface F2. The pair of side end guides34and the rearward end guide53are moved according to the size of the sheets P to be placed.

Structural detail of the lever section70will be described with reference toFIGS. 2 and 3. InFIGS. 2 and 3, the lever section70is in the first engaged position. The lever section70is formed integrally with the bottom member50. The lever section70is plate-like. The lever section70is formed from an elastic material or formed to have elasticity. Thus, it is possible to easily form the lever section70that can be shifted upward and downward.

The lower portion75of the lever section70is located higher than the bottom member30and lower than the bottom member50, and is substantially parallel to the bottom member50and to the bottom member30. The projected portion76of the lever section70has a curved outer edge. The projected portion76is formed continuous from one end (more specifically, a rearward end) of the lower portion75. The projected portion76is inclined relative to the lower portion75and projected in a diagonal upward direction from the lower portion75toward the extending direction A1. The projected portion76protrudes from the sheet loading surface F2of the bottom member50by a distance d1.

The lever section70has a cylindrical through hole74to be caught by a finger of a user. The finger catches in the through hole74at a side thereof corresponding to the projected portion76. More specifically, the through hole74is formed in the lever section70so as to span across the lower portion75and the projected portion76. The through hole74penetrates through an upper surface and a lower surface of the lever section70.

The lever section70has a second opposed region77that is opposed to a first opposed region37according to a position of the lever section70. The lower surface of the lower portion75of the lever section70is the second opposed region77. The mating engagement pawl78ais formed in the second opposed region77. It should be noted that the main cassette3has the first opposed region37that is opposed to the lever section70according to the position of the lever section70. The engagement pawl38ais formed in the first opposed region37.

One end (more specifically, a rearward end) of the proximal end portion72is connected with the other end (more specifically, the forward end) of the lower portion75. The other end (more specifically, a forward end) of the proximal end portion72is connected with the bottom member50. The proximal end portion72is inclined downward from the bottom member50toward the lower portion75. The lower portion75is therefore disposed at a position lower than the sheet loading surface F2of the bottom member50by a distance d2.

Shift of the lever section70will be described with reference toFIGS. 3 and 4. As illustrated inFIG. 3, the lever section70is in the first engaged position while no sheets P are loaded in the sheet cassette1and no external force is exerted on the projected portion76. As illustrated inFIG. 4, the lever section70is shifted from the first engaged position to the disengaged position when external force in the upward direction B1is exerted on the projected portion76and thus the projected portion76is pulled up. That is, the lever section70is shifted to the disengaged position when no sheets P are loaded in the sheet cassette1and external force in the upward direction B1is exerted on the projected portion76.

More specifically, the projected portion76is a free end portion. Therefore, the external force shifts the lever section70in the upward direction B1about the proximal end portion72from the first engaged position to the disengaged position. When the external force is released while the lever section70is in the disengaged position, the projected portion76is lowered due to the elasticity of the proximal end portion72such that the lever section70is shifted back to the first engaged position.

The user can put a finger in the through hole74, catch the projected portion76with the finger, and pull up the projected portion76in the upward direction B1. As a result, the user can shift the lever section70into the disengaged position. The user can then release the finger from the lever section70or relax the force thereby to let the projected portion76move in the downward direction B2so that the lever section70is shifted from the disengaged position back to the first engaged position.

Structure of the engagement pawl38aand the mating engagement pawl78awill be described with reference toFIG. 3. The engagement pawl38aprojects from the bottom member30of the main cassette3. More specifically, the engagement pawl38aprojects from the first opposed region37. The engagement pawl38ahas an engagement surface38cand an inclined surface38d. The inclined surface38dis on an opposite side of the engagement pawl38ato the engagement surface38c. The inclined surface38dis inclined upward in the contracting direction A2from the first opposed region37.

The mating engagement pawl78aprojects from the lever section70of the sliding cassette5. More specifically, the mating engagement pawl78aprojects from the second opposed region77. The mating engagement pawl78ahas an engagement surface78cand an inclined surface78d. The inclined surface78dis on an opposite side of the mating engagement pawl78ato the engagement surface78c. The inclined surface78dis inclined downward in the extending direction A1from the second opposed region77.

[Restriction of Sliding of Sliding Cassette5]

Restriction of the sliding of the sliding cassette5will be described with reference toFIGS. 3 and 6. First, restriction of the sliding when the lever section70is in the first engaged position will be described. While the lever section70is in the first engaged position at an engagement point, the engagement pawl38aand the mating engagement pawl78aare in engagement. The engagement point is where the engagement pawl38ais opposite to the mating engagement pawl78a. More specifically, the engagement surface38cand the engagement surface78care in engagement. Accordingly, the sliding of the sliding cassette5in the extending direction A1is restricted. The position of the sliding cassette5with the engagement pawl38aand the mating engagement pawl78ain engagement is a position where the sliding cassette5is pushed in the contracting direction A2to the maximum, that is, the retracted position. Accordingly, the sliding cassette5is locked in a position where the size of the sheet cassette1is a minimum size.

Next, restriction of the sliding in a situation in which the sheets P are loaded in the sheet cassette1will be described. The lever section70is in the first engaged position before the sheets P are loaded in the sheet cassette1. Once the sheets P are loaded in the sheet cassette1, the projected portion76in contact with the sheets P receives the weight of the sheets P. The lever section70is therefore pushed down by the sheets P and shifted to the second engaged position. That is, the weight of the sheets P shifts the lever section70in the downward direction B2about the proximal end portion72to the second engaged position. The distance of the shift of the lever section70can increase up to the distance d1(seeFIG. 3) with increase in the weight of the sheets loaded. Strength of the engagement between the engagement pawl38aand the mating engagement pawl78atherefore increases with increase in the weight of the sheets loaded. The strength of the engagement is increased for the following reason.

Generally, sheets loaded in a sheet cassette move in a sheet cassette moving direction when the sheet cassette is inserted into an image forming apparatus. The moving sheets are received by a rearward end and a rearward end guide of the sliding cassette. Consequently, a load according to the weight of the sheets is placed on the rearward end and the rearward end guide. In particular, in a situation in which many sheets are loaded or sheets having a larger size are loaded, the load on the rearward end and the rearward end guide is larger. As a result, the sliding cassette may be unintendedly unlocked.

In the first embodiment, shift of the lever section70to the second engaged position allows the strength of the engagement between the engagement pawl38aand the mating engagement pawl78ato increase with increase in the weight of the sheets loaded, preventing unlocking of the sliding cassette5due to a load resulting from the movement of the sheets P.

Once the projected portion76of the lever section70is shifted in the downward direction B2by the distance d1, the sheets P become supported by the sheet loading surface F2of the sliding cassette5. Thus, the projected portion76is prevented from being further shifted in the downward direction B2by more than the distance d1. As a result, deformation or damage that prevents the lever section70from returning to the first engaged position can be restricted.

[Removal of Restriction of Sliding of Sliding Cassette5]

Removal of restriction of the sliding of the sliding cassette5will be described with reference toFIGS. 3 and 4. When external force in the upward direction B1is exerted on the projected portion76of the lever section70, and thus the lever section70is shifted from the position with the engagement pawl38aand the mating engagement pawl78ain engagement to the disengaged position, the mating engagement pawl78adisengages from the engagement pawl38athereby to release the engagement therebetween. Thus, the restriction of the sliding of the sliding cassette5is removed. That is, the sliding cassette5is unlocked. When external force in the extending direction A1is exerted on the lever section70, the sliding cassette5slides in the extending direction A1. The sliding cassette5is drawn in the extending direction A1to the maximum and locked by the second restricting section21in a position where the size of the sheet cassette1is a maximum size, that is, in the extended position.

A user for example extends the size of the sheet cassette1according to the following procedure. The user puts a finger in the through hole74, catches the projected portion76of the lever section70with the finger, and pulls up the projected portion76. As a result, the lever section70is shifted to the disengaged position, the engagement is released, and the restriction of the sliding is removed. Subsequently to the removal of the restriction of the sliding, the user catches a rear-side opening edge of the through hole74with a finger and pulls the finger in the extending direction A1. Consequently, the sliding cassette5can be drawn, and the size of the sheet cassette1can be extended. The sliding cassette5is drawn out by a prescribed distance, and stopped and locked by the second restricting section21.

A user for example contracts the size of the sheet cassette1according to the following procedure. The user pushes in the sliding cassette5in the contracting direction A2until the mating engagement pawl78acomes in engagement with the engagement pawl38a. Since the engagement pawl38ahas the inclined surface38dand the mating engagement pawl78ahas the inclined surface78d, the mating engagement pawl78acan smoothly engage with the engagement pawl38aas a result of the sliding of the sliding cassette5in the contracting direction A2.

A structure of the cutout portion39will be described with reference toFIGS. 2 and 3. The bottom member30of the main cassette3has the cutout portion39. More specifically, the cutout portion39extends in the extending direction A1from a specified location in the bottom member30to a rearward end of the bottom member30. The cutout portion39is formed by cutting out a U-shaped portion from a rearward end portion of the bottom member30. The cutout portion39is formed corresponding to a region of movement of the through hole74in accompaniment to the sliding of the sliding cassette5. Accordingly, the through hole74moves above the cutout portion39in accompaniment to the sliding of the sliding cassette5in the extending direction A1or in the contracting direction A2. As a result, the user can avoid contact of their finger with the bottom member30of the main cassette3and slide the sliding cassette5without pulling the finger out of the through hole74. In the first embodiment, the cutout portion39is formed by cutting out a U-shaped portion from the rearward end portion of the bottom member30.

According to the first embodiment, it is possible to adjust the size of the sheet cassette1by simple manipulation and restrict release of the locked state of the main cassette3and the sliding cassette5after loading of the sheets P as described above with reference toFIGS. 1 to 6.

Furthermore, according to the first embodiment, the engagement pawl38acan be formed integrally with the main cassette3, and the lever section70and the mating engagement pawl78acan be formed integrally with the sliding cassette5as described with reference toFIGS. 2 and 3. It is therefore possible to form a mechanism for unlocking the sliding cassette5with a reduced number of elements.

Furthermore, according to the first embodiment, the engagement pawl38aand the mating engagement pawl78aallow the locking and the unlocking of the sliding cassette5to be readily performed as described with reference toFIGS. 3 and 4.

Furthermore, according to the first embodiment, the lever section70has the through hole74as described with reference toFIG. 2. Accordingly, a user can readily unlock the sliding cassette5by putting a finger in the through hole74and pulling up the lever section70.

Second Embodiment

The sheet cassette1according to the second embodiment of the present invention will be described with reference toFIGS. 1, 2, and 7 to 9. Configuration of the sheet cassette1according to the second embodiment is the same as the configuration of the sheet cassette1according to the first embodiment except a part of the first restricting section7. Therefore, the sheet cassette1illustrated inFIGS. 1 and 2will be described as the sheet cassette1according to the second embodiment. Hereinafter, a difference between the second embodiment and the first embodiment will be mainly described.

FIG. 7is a cross-sectional view taken along line VII-VII inFIG. 2, illustrating the engaged state of the first restricting section7in the sheet cassette1adjusted to a small size. InFIG. 7, the sliding cassette5is in the retracted position, and the lever section70is in the first engaged position. The first restricting section7(restricting section) includes a plurality of engagement holes38b(a plurality of first engagement sections), the lever section70, and an engagement protrusion78b(second engagement section). In the second embodiment, the plurality of engagement holes38bare provided instead of the engagement pawl38a(seeFIG. 3) of the first embodiment, and the engagement protrusion78bis provided instead of the mating engagement pawl78a(seeFIG. 3) of the first embodiment.

The engagement holes38bfunction as locking portions. The plurality of engagement holes38bare three engagement holes38bin the second embodiment. Of the three engagement holes38b, an engagement hole38bclosest to the rearward end of the bottom member30may be referred to as an engagement hole38b1, an engagement hole38badjacent to the engagement hole38b1may be referred to as an engagement hole38b2, and an engagement hole38bfarthest from the rearward end of the bottom member30may be referred to as an engagement hole38b3. The configuration of the lever section70is the same as the configuration of the lever section70of the first embodiment (seeFIG. 3).

In the second embodiment, the first engaged position is a position where while the sliding cassette5is in the retracted position, no sheets are loaded on the bottom member50, the projected portion76protrudes from the sheet loading surface F2of the bottom member50, and the engagement protrusion78bis in engagement with one of the engagement holes38b. The second engaged position is a position where while the sliding cassette5is in the retracted position, the projected portion76is pushed down out of the first engaged position in accordance with the number of sheets loaded on the bottom member50, and the engagement hole38band the engagement protrusion78bare in engagement. The disengaged position is a position where while the sliding cassette5is in the retracted position, the lever section70is lifted out of the first engaged position, and thus the engagement between the engagement hole38band the engagement protrusion78bis released.

The plurality of engagement holes38bare formed in the bottom member30of the main cassette3. More specifically, the plurality of engagement holes38bare formed in the first opposed region37. In the second embodiment, each of the plurality of engagement holes38bis a cylindrical through hole. Alternatively, each of the plurality of engagement holes38bmay be a bottomed recess. The plurality of engagement holes38bare arranged along the extending direction A1.

Locations of the engagement holes38bare determined according to a maximum size of sheets P that can be loaded in the sheet cassette1while the engagement protrusion78band one of the engagement holes38bare in engagement. The engagement protrusion78bprotrudes from the lever section70of the sliding cassette5. More specifically, the engagement protrusion78bprotrudes from the second opposed region77. The engagement protrusion78bhas a cylindrical shape that can mate with each of the engagement holes38b. The engagement holes38btherefore have a slightly larger diameter than a diameter of the engagement protrusion78b.

First, restriction of sliding by engagement (mating) between the engagement holes38band the engagement protrusion78bwhen the lever section70is in the first engaged position will be described. While the lever section70is in the first engaged position at an engagement point, the engagement protrusion78bis in engagement with one of the engagement holes38b. The engagement point is where the one of the engagement holes38bis opposite to the engagement protrusion78b. More specifically, the engagement protrusion78bis mating with one of the engagement holes38b. Accordingly, the sliding of the sliding cassette5in the extending direction A1and in the contracting direction A2is restricted, and the sliding cassette5is locked. In the second embodiment, the term engagement and the term mating have the same meaning.

Next, restriction of the sliding in a situation in which the sheets P are loaded in the sheet cassette1will be described.FIG. 8illustrates a cross-section of the first restricting section7when the lever section70is in the second engaged position. InFIG. 8, a plurality of sheets P are loaded in the sheet cassette1, and the sliding cassette5is in the retracted position.

As in the first embodiment, the projected portion76is pushed down by the weight of the sheets P, and the lever section70is shifted in the downward direction B2about the proximal end portion72to the second engaged position. Strength of the engagement between the engagement hole38band the engagement protrusion78bis larger when the lever section70is in the second engaged position than when the lever section70is in the first engaged position.FIG. 8illustrates a situation in which the projected portion76is retracted below the sheet loading surface F2and the engagement strength is at its maximum.

More specifically, the distance of the shift of the lever section70can increase up to the distance d1(seeFIG. 7) with increase in the weight of the sheets loaded. Thus, the engagement protrusion78bmates with the engagement hole38bmore deeply when the lever section70is in the second engaged position than when the lever section70is in the first engaged position, and strength of the engagement between the engagement hole38band the engagement protrusion78bincreases with increase in the weight of the sheets loaded. As a result, as in the first embodiment, unlocking of the sliding cassette5due to a load resulting from the movement of the sheets P can be prevented. Since the projected portion76is not shifted downward by more than the distance d1as in the first embodiment, deformation or damage that prevents the lever section70from returning to the first engaged position can be restricted.

Next, adjustment of the size of the sheet cassette1will be described. Since there are three engagement holes38b1to38b3in the second embodiment, the sheet cassette1is adjustable to three different sizes. The three different sizes are a large size, a medium size, and a small size. The sliding cassette5is in the retracted position when the sheet cassette1is in the small size, in the first extended position when in the medium size, and in the second extended position when in the large size.

The small size of the sheet cassette1will be described with reference toFIGS. 7 and 8. The engagement protrusion78bis caused to mate with the engagement hole38b3by positioning the lever section70in the first engaged position or in the second engaged position. Accordingly, the sliding cassette5is in a position where the sliding cassette5is pushed in the contracting direction A2to the maximum. As a result, the sliding cassette5is locked in a position where the sheet cassette1is in the small size.

Although not shown, the sliding cassette5is locked in a position where the sheet cassette1is in the medium size when the engagement protrusion78bis mating with the engagement hole38b2and the sliding cassette5is locked in a position where the sheet cassette1is in the large size when the engagement protrusion78bis mating with the engagement hole38b1, with the lever section70in the first engaged position or in the second engaged position.

The second restricting section21(seeFIGS. 1 and 5) in the second embodiment has a pair of engagement holes41and a pair of engagement protrusions61formed according to the position of the engagement hole38b2, and another pair of engagement holes41and another pair of engagement protrusions61formed according to the position of the engagement hole38b1. Accordingly, when the engagement protrusion78bis mating with the engagement hole38b2, the pair of engagement holes41and the pair of engagement protrusions61formed according to the position of the engagement hole28b2are mating with one another to lock the sliding cassette5in the position where the sheet cassette1is in the medium size. When the engagement protrusion78bis mating with the engagement hole38b1, the pair of engagement holes41and the pair of engagement protrusions61formed according to the position of the engagement hole38b1are mating with one another to lock the sliding cassette5in the position where the sheet cassette1is in the large size.

Next, removal of the restriction of the sliding by releasing the engagement (releasing the mating) between one of the engagement holes38band the engagement protrusion78bwill be described.FIG. 9is a cross-sectional view illustrating the disengaged state. InFIG. 9, the lever section70is in the disengaged position. Once external force in the upward direction B1is exerted on the projected portion76of the lever section70in the first engaged position with the engagement protrusion78bmating with one engagement hole38b, the lever section70is shifted to the disengaged position, and thus the engagement protrusion78bis pulled out of the engagement hole38b, releasing the mating therebetween. Thus, the restriction of the sliding of the sliding cassette5is removed. That is, the sliding cassette5is unlocked.

When external force in the extending direction A1is subsequently exerted on the lever section70, the sliding cassette5slides in the extending direction A1. Once the lever section70is shifted to the first engaged position after the sliding cassette5has been drawn in the extending direction A1, the engagement protrusion78bmates with another engagement hole38b. As a result, the sliding is once again restricted, and the sliding cassette5is locked.

When external force in the contracting direction A2is exerted on the lever section70after release of the mating, the sliding cassette5slides in the contracting direction A2. Once the lever section70is shifted to the first engaged position after the sliding cassette5has been pushed in the contracting direction A2, the engagement protrusion78bmates with yet another engagement hole38b. As a result, the sliding is once again restricted, and the sliding cassette5is locked.

A user for example extends or contracts the size of the sheet cassette1according to the following procedure. The user puts a finger in the through hole74, catches the projected portion76of the lever section70with the finger, and pulls up the projected portion76. As a result, the lever section70is shifted to the disengaged position, the mating between the engagement protrusion78band one engagement hole38bis released, and the restriction of the sliding is removed. Subsequently to the removal of the restriction of the sliding, the user catches the rear-side opening edge of the through hole74with a finger and pulls the finger in the extending direction A1or pushes the projected portion76of the lever section70in the contracting direction A2. As a result, the sliding cassette5is drawn out or pushed in. The user subsequently causes the engagement protrusion78bto mate with another engagement hole38b, thereby locking the sliding cassette5and extending or contracting the size of the sheet cassette1.

According to the second embodiment, it is possible to adjust the size of the sheet cassette1by simple manipulation and restrict release of the locked state of the main cassette3and the sliding cassette5after loading of the sheets P as described above with reference toFIGS. 1, 2, and 7 to 9. The second embodiment further produces the following effect in addition to the same effect as produced by the first embodiment.

That is, according to the second embodiment, the engagement holes38bare formed by processing the main cassette3, and the lever section70and the engagement protrusion78bcan be formed integrally with the sliding cassette5as described with reference toFIG. 7. It is therefore possible to form a mechanism for unlocking the sliding cassette5with a reduced number of elements.

Furthermore, the second embodiment includes a plurality of engagement holes38b. The plurality of engagement holes38bare arranged along the extending direction A1. Thus, the sheet cassette1is adjustable to a plurality of different sizes.

Furthermore, according to the second embodiment, the engagement protrusion78band the engagement holes38ballow the locking and the unlocking of the sliding cassette5to be readily performed.

Third Embodiment

The sheet cassette1according to the third embodiment of the present invention will be described with reference toFIGS. 1, 2, and 10. Configuration of the sheet cassette1according to the third embodiment is the same as the configuration of the sheet cassette1according to the first embodiment except a part of the first restricting section7. Therefore, the sheet cassette1illustrated inFIGS. 1 and 2will be described as the sheet cassette1according to the third embodiment. Hereinafter, a difference between the third embodiment and the first embodiment will be mainly described.

FIG. 10Ais a cross-sectional view illustrating the engaged state of the first restricting section7(restricting section).FIG. 10Aillustrates the lever section70in the first engaged position.

In the third embodiment, a plurality of engagement pawls38e(a plurality of first engagement sections) are provided instead of the engagement pawl38a(seeFIG. 3) of the first embodiment. Furthermore, the main cassette3includes a rack73. The rack73is disposed in the bottom member30of the main cassette3and is movable relative to the main cassette3in a sliding direction of the sliding cassette5. The sliding direction is the extending direction A1or the contracting direction A2. The rack73has the plurality of engagement pawls38earranged in the sliding direction of the sliding cassette5. As described above, an engagement structure that is engageable with the mating engagement pawl78ais formed from the rack73having the plurality of engagement pawls38earranged in the sliding direction. The rack73has the first opposed region37that is opposed to the lever section70according to the position of the lever section70. The engagement pawls38eare formed in the first opposed region37.

FIG. 10Bis a schematic view illustrating the rack73. Each engagement pawl38ehas a different length from a peak thereof to a peak of the mating engagement pawl78a(hereinafter, referred to as an “engagement length”) when the lever section70is in the first engaged position. In the third embodiment, the plurality of engagement pawls38ehave protrusion amounts that increase stepwise in the extending direction A1. Detailed description thereof will be given below.

In the third embodiment, engagement pawls38e1to38e3are provided as the plurality of engagement pawls38e. Of engagement lengths D1to D3, the engagement length D1of the engagement pawl38e1is the longest, the engagement length D3of the engagement pawl38e3is the shortest, and the engagement length D2of the engagement pawl38e2is between the engagement length D1and the engagement length D3.

The longer the engagement length of an engagement pawl38eis, the stronger the engagement between the engagement pawl38eand the mating engagement pawl78ais, and the tighter the locking of the sliding cassette5is. By contrast, the shorter the engagement length of an engagement pawl38eis, the looser the locking of the sliding cassette5is, but the more operable the sliding cassette5is. That is, the easier unlocking and sliding the sliding cassette5is.

The rack73is secured to the bottom member30with an engagement surface38cof one of the engagement pawls38e1to38e3at an engagement location E. In the third embodiment, therefore, a user can adjust the tightness of the locking of the sliding cassette5and the operability of the sliding cassette5to different degrees according to usage conditions by moving the rack73.

In a situation in which the sheet cassette1is used frequently by being filled with sheets P having a maximum size, for example, the user adjusts the position of the rack73so that the locking is tight. For example, the rack73is fixed so that the engagement pawl38e1is at the engagement location E. On the other hand, in a situation in which the sheet cassette1is used less frequently by being filled with sheets P having a maximum size, for example, the user adjusts the position of the rack73so that the locking is loose, giving priority to the operability. For example, the rack73is fixed so that the engagement pawl38e3is at the engagement location E.

Since the third embodiment has the same lever section70as the first embodiment, it is possible to adjust the size of the sheet cassette1by simple manipulation and restrict release of the locked state of the main cassette3and the sliding cassette5after loading of the sheets P.

In the third embodiment, the first engaged position is a position where while the sliding cassette5is in the retracted position, no sheets are loaded on the bottom member50, the projected portion76protrudes from the sheet loading surface F2of the bottom member50, and one engagement pawl38eand the mating engagement pawl78aare in engagement. The second engaged position is a position where while the sliding cassette5is in the retracted position, the projected portion76is pushed down out of the first engaged position in accordance with the number of sheets loaded on the bottom member50, and the engagement pawl38eand the mating engagement pawl78aare in engagement. The disengaged position is a position where while the sliding cassette5is in the retracted position, the lever section70is lifted out of the first engaged position, and thus the engagement between the engagement pawl38eand the mating engagement pawl78ais released.

Fourth Embodiment

An image forming apparatus100in the fourth embodiment of the present invention will be described with reference toFIG. 11.FIG. 11is a schematic cross-sectional view for illustrating an overview of the image forming apparatus100. The image forming apparatus100is for example a copier, a printer, or a multifunction peripheral. A multifunction peripheral for example has at least two of a copier, a printer, and a facsimile machine. Hereinafter, an example in which the image forming apparatus100is a printer will be described.

The image forming apparatus100includes a feeder10, an image forming section80, and a discharge section90. The image forming apparatus100also has a conveyance path L. The conveyance path L includes conveyance paths L1to L3and a conveyance path Lb.

The feeder10includes the sheet cassette1, a feeding section2, and a manual feed tray9. The sheet cassette1is the sheet cassette1according to the first embodiment (seeFIG. 3), the sheet cassette1according to the second embodiment (seeFIG. 7), or the sheet cassette1according to the third embodiment (seeFIG. 10). The sheet cassette1is disposed in a lower part of the image forming apparatus100. The sheet cassette1is drawable from a front surface of the image forming apparatus100in a negative direction of the X axis along the X axis. The panel33of the sheet cassette1forms a portion of the front surface of the image forming apparatus100.

The feeding section2feeds the sheets P loaded in the sheet cassette1. More specifically, the feeding section2includes a pickup roller4and a pair of feeding rollers6. The pair of feeding rollers6include a retard roller6aand a feed roller6b. The pickup roller4feeds the sheets P loaded in the sheet cassette1to the pair of feeding rollers6while rotating.

The pair of feeding rollers6prevent multiple feeding of sheets P and feed the sheets P to the conveyance path L1one sheet at a time. More specifically, the feed roller6bfeeds the sheets P while rotating. When receiving one sheet P, the retard roller6ais driven to rotate by the feed roller6b. When receiving a plurality of sheets P stuck on one another, on the contrary, the retard roller6arotates in a direction opposite to a direction for feeding the sheets P or stops to separate a sheet P in contact with the feed roller6bfrom another sheet P. As a result, one sheet P is fed by the feed roller6b. The sheet P is conveyed to the image forming section80along the conveyance path L1. Sheets P are also loaded on the manual feed tray9. The sheets P are fed from the manual feed tray9to the conveyance path L2and further fed to the conveyance path L1. The sheets P are conveyed to the image forming section80along the conveyance path L1.

The image forming section80forms an image on a sheet P fed by the feeder10. More specifically, the image forming section80includes a photosensitive drum81, a charger82, a development section83, a transfer section84, a cleaning section85, a light exposure section86, a toner cartridge87, and a fixing section88.

The photosensitive drum81rotates in a direction along a conveyance direction C of the sheets P. The charger82charges a surface of the photosensitive drum81. The light exposure section86irradiates the surface of the photosensitive drum81with light based on image data. As a result, an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum81. The development section83attaches toner to the electrostatic latent image to form a toner image on the surface of the photosensitive drum81. The toner cartridge87contains the toner and supplies the toner to the development section83.

The transfer section84presses the sheet P against the surface of the photosensitive drum81to transfer the toner image onto the sheet P. The sheet P having the toner image transferred thereon is conveyed to the fixing section88along the conveyance path L2. The fixing section88applies heat and pressure to the sheet P to fix the toner image on the sheet P. The sheet P on which the toner image has been fixed by the fixing section88is conveyed to the discharge section90along the conveyance path L3. The cleaning section85removes toner left on the surface of the photosensitive drum81.

The discharge section90includes a pair of discharge rollers91and an exit tray92. The pair of discharge rollers91discharge the sheet P conveyed thereto along the conveyance path L3to the exit tray92. When duplex printing is to be performed, the sheet P conveyed to the conveyance path L3is returned into the conveyance path L1along the conveyance path Lb. The sheet P is for example plain paper, recycled paper, thin paper, thick paper, or an overhead projector (OHP) sheet.

As described above, the image forming apparatus100according to the fourth embodiment includes the sheet cassette1according to the first embodiment, the sheet cassette1according to the second embodiment, or the sheet cassette1according to the third embodiment. It is therefore possible to adjust the size of the sheet cassette1by simple manipulation and restrict release of the locked state of the main cassette3and the sliding cassette5after loading of the sheets P. Other than that, the third embodiment produces the same effects as the first embodiment, the second embodiment, and the third embodiment.

The embodiments of the present invention have been described so far with reference toFIGS. 1 to 11. However, the present invention is not limited to the above-described embodiments and can be practiced in various ways within the scope without departing from the essence of the present invention. For example, the following alterations may be made.

(1) The first embodiment includes a single engagement pawl38a. Alternatively, a plurality of engagement pawls38amay be formed. In this case, the plurality of engagement pawls38aare arranged parallel to the extending direction A1as in the case of the plurality of engagement holes38baccording to the second embodiment. Thus, the sheet cassette1is adjustable to a plurality of different sizes. Furthermore, the second embodiment may have a single engagement hole38b.

(2) The engagement between the engagement pawl38aand the mating engagement pawl78ais released, the engagement between one engagement hole38band the engagement protrusion78bis released, or the engagement between one engagement pawl38eand the mating engagement pawl78ais released by pulling up the lever section70in the upward direction B1in the first embodiment to the third embodiment. Alternatively, a configuration in which the engagement is released by pushing down the lever section70in the downward direction B2may be employed.

(3) A plurality of protrusions may be formed instead of the plurality of engagement holes38b, and an engagement hole may be formed instead of the engagement protrusion78bin the second embodiment.

(4) The cutout portion39is formed in the bottom member30of the main cassette3in the first embodiment to the third embodiment. Alternatively, the main cassette3may have a through hole instead of the cutout portion39. More specifically, the through hole is formed in the bottom member30corresponding to the region of movement of the through hole74in accompaniment to the sliding of the sliding cassette5. A user can therefore slide the sliding cassette5without pulling their finger out of the through hole74.

(5) The projected portion76is projected in a diagonal upward direction from the lower portion75toward the extending direction A1in the first embodiment to the third embodiment. Alternatively, the projected portion76may be projected in a diagonal upward direction from the lower portion75toward the contracting direction A2or projected in a vertical upward direction from the lower portion75.

(6) The rack73is movable relative to the main cassette3in the sliding direction of the sliding cassette5in the third embodiment. Alternatively, the rack73may be fixed to the bottom member30so as to be non-movable relative to the main cassette3. Accordingly, the lever section70is disposed in the sliding cassette5so as to be movable relative to the sliding cassette5in the sliding direction of the sliding cassette5. As a result, it is possible to adjust the tightness of the locking of the sliding cassette5and the operability of the sliding cassette5to different degrees according to usage conditions as in the third embodiment.

(7) The lever section70is formed from an elastic material or formed so as to have elasticity in the first embodiment to the third embodiment. The lever section70may be formed as a separate member from the sliding cassette5and connected with the bottom member50. Examples of elastic materials include synthetic resins and metals. Examples of the lever section70formed so as to have elasticity include a plate spring.

(8) The sheet conveyance direction in the sheet cassette1is substantially the same as the contracting direction A2in the first embodiment to the fourth embodiment. Alternatively, the sheet conveyance direction may be different from the contracting direction A2. For example, the sheet conveyance direction may be substantially perpendicular to the contracting direction A2.

INDUSTRIAL APPLICABILITY

The present invention is applicable to the fields of sheet cassettes in which a plurality of sheets are loaded, and of feeders and image forming apparatuses including the sheet cassettes.