Stacking apparatus, feeding apparatus, and image forming apparatus

A stacking apparatus includes a limiting member which moves along a feeding direction and limits a trailing edge of a stacked sheet in the feeding direction, and a partition member which partitions a space at a height which is lower than a predetermined height, into a first space corresponding to a first stacking unit and a second space corresponding to a second stacking unit in a feeding direction. The partition member includes a first opening portion for communicating the first space and the second space with each other, and a second opening portion that allows the limiting member to move.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a stacking apparatus, a feeding apparatus, and an image forming apparatus capable of stacking a sheet as an image forming target.

Description of the Related Art

Some image forming apparatuses such as a copying machine and printer have an arrangement which includes a sheet storage unit and a feeding unit such as a feeding roller for feeding sheets stored in the sheet storage unit, and feeds a sheet stored in the sheet storage unit to an image forming unit by the feeding unit. Recently, image forming apparatuses including a large-capacity sheet storage unit into which a large number of sheets such as thousands of sheets can be replenished are increasing in number. Also, in the recent printing market, needs for performing printing on elongated paper sheets longer than regular-size paper sheets such as A3 and A4 are increasing (for example, a book cover, facing pages of a catalogue, and POP advertisement).

In a conventional sheet feeding apparatus that supports elongated paper sheets, a plurality of paper stacking lifters which are independently operable are arranged, and removable partition plates are provided in common use. Each partition plate has a function of preventing stacked sheets from collapsing or mixing in size (Japanese Patent Laid-Open No. 2003-63719).

In a conventional arrangement, however, if a partition plate is removed when a user uses a paper stacking lifter on one side, he/she needs to attach the partition plate again, impairing usability. Moreover, if an elongated paper sheet is to be fed in a state in which the partition plate is always mounted, an internal atmosphere between the paper stacking lifters is blocked. That is, a recent feeding apparatus needs to support various paper types, and as measures against paper having a high friction coefficient among pieces of paper, such as coated paper in particular, an air flow may be generated inside by using, for example, a heat source such as a cassette heater, a fan, or the like. In the conventional arrangement, however, internal air permeability becomes deteriorated due to the partition plate, so heat or the internal air flow cannot be circulated well.

SUMMARY OF THE INVENTION

The present invention provides a stacking apparatus, a feeding apparatus, and an image forming apparatus capable of keeping air permeability satisfactorily while improving usability with a simple arrangement.

The present invention in one aspect provides a stacking apparatus capable of stacking, as a sheet fed to a predetermined apparatus, a first sheet and a second sheet having a larger size than the first sheet in a feeding direction in which the sheet are fed to the predetermined apparatus, the stacking apparatus comprising: a first stacking unit configured to stack the first sheet; a second stacking unit configured to be able to move at a height which is equal to or higher than a predetermined height and stack the second sheet in cooperation with the first stacking unit at a height which is equal to or higher than the predetermined height; a limiting unit configured to move along the feeding direction and limit a trailing edge of a stacked sheet in the feeding direction; and a partition member configured to partition a space at a height which is lower than the predetermined height, into a first space corresponding to the first stacking unit and a second space corresponding to the second stacking unit in the feeding direction, wherein the partition member includes a first opening portion for communicating the first space and the second space with each other, and a second opening portion that allows the limiting unit to move.

The present invention can keep air permeability satisfactory while improving usability with the simple arrangement.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a schematic sectional view showing an image forming apparatus including a sheet feeding apparatus according to an embodiment of the present invention. An image forming system1000includes an image forming apparatus900, a scanner apparatus2000arranged on the upper surface of the image forming apparatus900, and a paper deck3000connected to the image forming apparatus900.

The scanner apparatus2000, which reads a document, includes a scanning optical system light source201, a platen glass202, an openable/closable document press plate203, a lens204, a light-receiving element (photoelectric conversion element)205, an image processor206, a memory unit208, and the like. The memory unit208stores an image processing signal processed by the image processor206.

When reading a document, the scanner apparatus2000reads a document (not shown) placed on the platen glass202by irradiating the document with light from the scanning optical system light source201. A read document image is processed by the image processor206, converted into an electrical signal207which is electrically encoded, and transmitted to a laser scanner111in the image forming apparatus900.

Note that it is also possible to temporarily store the image information processed by the image processor206and encoded in the memory unit208, and transmit the stored information to the laser scanner111as needed in accordance with a signal from a controller120(to be described later). Note also that the paper deck3000includes a control unit41which controls the paper deck3000in accordance with a command from the controller120, and includes a CPU, a RAM, and a ROM.

The image forming apparatus900includes first to fourth sheet feeding apparatuses1001to1004for feeding sheets S, and a sheet conveying apparatus902for conveying the sheets S fed from the sheet feeding apparatuses1001to1004to an image forming unit901. The image forming apparatus900includes the controller120which controls the individual units of the image forming system1000, and includes a CPU, a RAM, and a ROM.

Each of the first to fourth sheet feeding apparatuses1001to1004includes a feeding cassette10for storing the sheets S, a pickup roller11, and a separation conveyor roller pair25including a feed roller22and a retard roller23. The sheets S stored in the feeding cassette10are separately fed one by one by the pickup roller11which performs a vertical moving operation and rotates at a predetermined timing, and the separation conveyor roller pair25.

In addition, a feed sensor24is arranged near the downstream side of the feed roller22and retard roller23in the sheet feeding direction. The feed sensor24senses the passing of the sheet S, and transmits a sensing signal to the controller120.

The sheet conveying apparatus902includes a conveyor roller pair15, a pre-registration roller pair130, and a registration roller pair110. The sheet S fed from the sheet feeding apparatuses1001to1004is passed through a sheet conveyance path108by the conveyor roller pair15and the pre-registration roller pair130, and guided to the registration roller pair110. After that, the registration roller pair110supplies the sheet S to the image forming unit901at a predetermined timing.

The image forming unit901includes a photosensitive drum112, the laser scanner111, a developing device114, a transfer charging device115, a separation charging device116, and the like. In image formation, a mirror113reflects a laser beam from the laser scanner111, and the photosensitive drum112rotating clockwise is irradiated with the laser beam, thereby forming an electrostatic latent image on the photosensitive drum. Then, the electrostatic latent image formed on the photosensitive drum is developed as a toner image by the developing device114.

This toner image on the photosensitive drum is transferred onto the sheet S by the transfer charging device115in a transfer unit112b. Furthermore, the sheet S onto which the toner image is thus transferred is electrostatically separated from the photosensitive drum112by the separation charging device116, conveyed by a conveyor belt117to a fixing apparatus118where the toner image is fixed, and then discharged by discharge rollers119. The image forming unit901and the fixing apparatus118form an image on the sheet S fed from a sheet feeding apparatus30(or the sheet feeding apparatuses1001to1004).

In addition, a discharge sensor122is arranged in a conveyance path between the fixing apparatus118and the discharger rollers119. The controller120detects the passing of the discharged sheet S based on a sensing signal from this discharge sensor122.

Note that the image forming apparatus900and the scanner apparatus2000are formed as discrete units in this embodiment, but the image forming apparatus900and the scanner apparatus2000may also be integrated. Note also that regardless of whether the image forming apparatus900and the scanner apparatus2000are separated or integrated, the image forming apparatus900functions as a copying machine when a processing signal of the scanner apparatus2000is input to the laser scanner111, and functions as a FAX apparatus when a FAX transmission signal is input to the laser scanner111. Furthermore, the image forming apparatus900also functions as a printer when a signal from a personal computer (PC) is input to the image forming apparatus900.

Conversely, the image processing apparatus900functions as a FAX apparatus when transmitting a processing signal of the image processor206of the scanner apparatus2000is transmitted to another FAX apparatus. In addition, if an automatic document feeder (ADF)250as indicated by the alternate long and two short dashed lines is used instead of the press plate203in the scanner apparatus2000, documents (not shown) can be fed and read in succession.

Next, the sheet feeding apparatus30of the image forming system1000according to this embodiment will be explained by taking the paper deck3000as a large-capacity deck as an example.FIG. 2is a perspective view showing main parts of the paper deck3000with an exterior cover being removed.

As shown inFIGS. 1 and 2, the paper deck3000includes a main body3000a, a large-capacity deck storage62accommodated in the main body3000a, and the sheet feeding apparatus30. This sheet feeding apparatus30feeds the sheets S stacked and accommodated in the large-capacity deck storage62to the image forming unit901.

The sheet feeding apparatus30includes a pickup roller51for feeding the sheets S stacked in a main lifter61a(first stacking unit) on which sheets SS of regular-size paper (to be referred to as plain paper hereinafter) are stacked and an extension lifter61b(second stacking unit) which is used to feed sheets SL of large-size paper (elongated paper) (to be referred to as a lifter61altogether hereinafter), and a separation conveyor roller pair31which are formed by a feed roller12and a retard roller13. The extension lifter61bis used to extend a stacking area of the main lifter61aonto a conveyance direction. The pickup roller51is arranged to be able to come into pressure contact with the uppermost sheet on the lifter61by applying an appropriate force to the sheet near the distal end portion in the sheet feeding direction (the direction of an arrow b). The pickup roller51is positioned above the lifter61, abuts against the uppermost one of the sheets S stacked on the lifter61having moved upward, and feeds the uppermost sheet.

Sheets can be stacked on the lifter61. The lifter61is supported by a driving mechanism54(FIG. 6) including a vertical movement motor55so as to be movable upward and downward. In addition, an upper surface sensor50is arranged on the upstream side of the pickup roller51above the lifter61. The upper surface sensor50is positioned above the lifter61, and senses the sheets S on the stacking member.

The sheet feeding apparatus30includes the lifter61, and two pairs of side limiting members80and83. The side limiting members80and83can limit the side edge positions of the sheets S stacked on the lifter61in the widthwise direction (the direction of an arrow h inFIG. 2) perpendicular to the feeding direction (the direction of the arrow b inFIG. 2), and both of the side limiting members80and83can move in the widthwise direction.

In this embodiment, the pickup roller51can come into pressure contact with the uppermost one of the sheets S on the stacking member by applying an appropriate force to the uppermost sheet. The sheets S on the lifter61are separately fed one by one by the pickup roller51which vertically moves and rotates at a predetermined timing and the separation conveyor roller pair31.

A connecting conveyance path32for feeding the sheet S from the paper deck3000to the pre-registration roller pair130of the image forming apparatus900is arranged in that portion of the paper deck3000, which is connected to the image forming apparatus900.

In the large-capacity deck storage62, the two pairs of side limiting members80and83arranged on the two sides in the direction (the widthwise direction in this embodiment) perpendicular to the sheet feeding direction (the direction of the arrow b) are arranged. The two pairs of side limiting members80and83can slide to the widths of all sheet sizes corresponding to the specifications, and can guide the sheets S on the lifter61. That is, the side limiting members80and83are so supported as to be movable in the widthwise direction, and limit the two side positions of the stacked sheets S by abutting against the two side edges of the sheets S. Note that a leading edge limiting member86inFIG. 2limits the leading edges of the sheets S on the lifter61.

Also, a trailing edge limiting member87is so arranged as to limit the trailing edges of the sheets S on the lifter61. The trailing edge limiting member87is so supported as to be movable parallel to the sheet feeding direction (the direction of the arrow b), and limits the trailing edge positions of the sheets S. The trailing edge limiting member87can move along a positioning elongated hole61c(FIG. 2) formed in the central portion of the lifter61.

As shown inFIG. 2, when the pickup roller51is driven by a driving unit (not shown) to rotate in the direction of feeding the sheets S (the direction of an arrow a), the uppermost sheet S is fed in the direction of the arrow b. Consequently, the sheet S abuts against the nip portion of the separation conveyor roller pair31adjacent to the exit side of the pickup roller51.

If multi feed occurs on the sheets S fed by the pickup roller51, the following operation is performed. That is, the retard roller13which rotates in the direction opposite to that of the feed roller12which rotates in the same direction (the direction of an arrow c) as the arrow a rotates in the same direction as that of the feed roller12if two or more sheets S abut against the nip portion. Then, the retard roller13pushes the second and subsequent sheets S in the nip portion back in the direction of the lifter61, and the feed roller12feeds only a single uppermost sheet S in the direction of the arrow b.

When the sheet S is fed from the paper deck3000having the above arrangement or from one of the first to fourth sheet feeding apparatuses1001to1004, the leading edge of the sheet S abuts against the nip portion of the pre-registration roller pair130. The pre-registration roller pair130includes a pair of opposite rollers, and is arranged on the conveyance path of the sheets S so as to be rotatable in the direction of an arrow d inFIG. 2by a driving unit (not shown). The sheet S which once abuts against the nip portion of the pre-registration roller pair130is conveyed into the image forming apparatus900by the roller pair130, which rotates in synchronism with the feed timing.

FIG. 5Ais a view showing a state in which the large-capacity deck storage62is retracted in the paper deck3000. A storage opening/closing button306is a button for accepting an instruction to pull out the large-capacity deck storage62. The large-capacity deck storage62can be pulled out when the user presses the storage opening/closing button306.FIG. 5Bis a view showing a state in which the large-capacity deck storage62is pulled out to the front side from the paper deck3000. The large-capacity deck storage62is pulled out as shown inFIG. 5Bwhen, for example, the user replenishes sheets, removes sheets remaining in the lifter61, or performs mode switching (to be described later). As will be described later, the paper deck3000includes an LED400for notifying the user of the states of the main lifter61aand extension lifter61b.

The lifter61includes the main lifter61aand the extension lifter61b. As shown inFIG. 2, a plurality of wires are connected to the wire fulcrums of the main lifter61a, and the main lifter61ais suspended by these wires. When the wires are wound by a winding unit connected to a motor, the lifter61moves upward. When the wires are fed, the lifter61moves downward.

The extension lifter61bis installed as it is supported by a partition plate350and the large-capacity deck storage62, as shown inFIGS. 2 and 3A. The extension lifter61bitself has no driving power. For example, when the main lifter61aexists above the support height of the extension lifter61b, the extension lifter61bis coupled with the main lifter61aand moves together with the main lifter61a. On the other hand, when the main lifter61aexists below the support height of the extension lifter61b, the extension lifter61bwaits at the support height.

This support height is set in consideration of the driving power and strength of the lifter61. This step between the lifters makes the number of elongated paper sheets SL to be stacked fall within the allowable range of the sheet feeding apparatus30.

FIG. 6is a view showing the block configuration of the image forming system1000for implementing the operation of this embodiment.FIG. 6shows the paper deck3000, the image forming apparatus900, and an operation panel40.

The operation panel40displays various user interface screens such as apparatus information, a setting screen, and job information, and accepts instructions and setting operations from the user. The operation panel40is formed on, for example, the image forming apparatus900. The image forming apparatus900issues a printing request to the control unit41of the paper deck3000. When receiving this printing request from the image forming apparatus900, the control unit41performs a feeding operation for the image forming apparatus900. Alternatively, the image forming apparatus900may include the control unit41.

The control unit41comprehensively controls the paper deck3000. For example, when receiving an opening request signal input by the user by pressing the storage opening/closing button306, the control unit41cancels the locked state of a storage lock solenoid46via a driver45, thereby opening the large-capacity deck storage62. The control unit41drives various motors44on the sheet conveyance path via a motor driver43connected to an input/output interface (I/O)42. Also, the control unit41controls the driving mechanism54for vertically moving the main lifter61aand the extension lifter61bvia a motor driver53connected to the input/output interface (I/O)42. The driving mechanism54includes the vertical movement motor55. The vertical movement motor55drives the winding unit (not shown).

Sensing signals from a relay sensor48, a storage opening/closing sensor401, the upper surface sensor50, and a sheet presence/absence sensor300are transmitted to the control unit41. The storage opening/closing sensor401is a sensor for sensing the opening/closing state of the storage. Sensing signals from a lower-limit position sensor301, a trailing edge limiting member position sensor302, a main lifter position sensor304, an extension lifter HP sensor303, and a foreign substance sensor49are transmitted to the control unit41. In addition, a storage opening request signal generated by the user by pressing the storage opening/closing button306is transmitted to the control unit41.

The control unit41controls lighting of the LED400by a lighting control signal. For example, in accordance with a plain paper mode/elongated paper mode, the control unit41controls lighting of the LED400based on a predetermined pattern.

A difference between two modes which the sheet feeding apparatus30uses in accordance with the types of sheets to be stacked will be explained below. In this embodiment, the types of sheets are roughly classified into two types. One is a plain paper sheet such as A3 and A4, and the other is an elongated paper sheet longer than the plain paper sheet in the feeding/conveyance direction. Sheets to be stacked on the lifter61are sorted into plain and elongated paper sheets in accordance with the position of the trailing edge limiting member87. A trailing edge limiting member position sensor302senses the position of the trailing edge limiting member87.

When the trailing edge limiting member87exists on the left side of the alternate long and short dashed line as shown inFIG. 4A, it is determined that sheets to be stacked on the lifter61are plain paper sheets. This state is called a plain paper mode. In this plain paper mode, as shown inFIG. 3A, the main lifter61acan move downward to a lower-limit position sensible by the illustrated lower-limit position sensor301, so a large amount of sheets can be stacked. For example, if the main lifter61amoves downward to a position sensible by the lower-limit position sensor301, 3,000 plain paper sheets can be stacked.

When the trailing edge limiting member87exists on the right side of the alternate long and short dashed line as shown inFIG. 4B, it is determined that sheets to be stacked on the lifter61are elongated paper sheets. This state will be called an elongated paper mode. In this elongated paper mode, as shown inFIG. 3B, the lifter61can move downward only to a position sensible by an extension lifter HP sensor303, so the number of stackable sheets is restricted compared to that of the plain paper mode. For example, while 3,000 plain paper sheets can be stacked, the number of stackable elongated paper sheets is limited to 1,000.

An operation when a user using an elongated paper sheet switches to use of a plain paper sheet will be described below with reference toFIG. 7. As described above, the elongated paper mode can be switched to the plain paper mode when the user moves the trailing edge limiting member87from the right side to the left side of the alternate long and short dashed line as shown inFIGS. 4A and 4B.

Processing inFIG. 7is started when the user presses the storage opening/closing button306. In step S101, the CPU41sets the large-capacity deck storage62in an open state (withdrawable state). In step S102, the CPU41determines whether the trailing edge limiting member position sensor302is in an ON state or an OFF state. If the CPU41determines here that the trailing edge limiting member position sensor302is in the ON state, the process advances to step S103. If the CPU41determines here that the trailing edge limiting member position sensor302is in the OFF state, the process advances to step S104. In step S103, the CPU41turns on the LED400and notifies the user that the elongated paper mode is set. A lighting pattern at this time is predetermined, and the user can identify that the elongated paper mode is set in accordance with the notification by the LED400. The process advances to step S104when the user moves the trailing edge limiting member87from the right side to the left side of the alternate long and short dashed line as shown inFIGS. 4A and 4B, and the CPU41detects that the trailing edge limiting member position sensor302is in the OFF state.

In step S104, when the user sets plain paper sheets, the CPU41detects that the plain paper sheets are set. Then, when the user closes the large-capacity deck storage62, in step S105, the CPU41detects that the large-capacity deck storage62is in a closed state. Subsequently, a feeding operation in the plain paper mode is started.

An operation when a user using a plain paper sheet switches to use of an elongated paper sheet will be described next with reference toFIG. 8. As described above, the plain paper mode can be switched to the elongated paper mode when the user moves the trailing edge limiting member87from the left side to the right side of the alternate long and short dashed line as shown inFIGS. 4A and 4B.

Processing inFIG. 8is started when the user presses the storage opening/closing button306. In step S201, the CPU41sets the large-capacity deck storage62in the open state (withdrawable state). In step S202, the CPU41determines whether the trailing edge limiting member position sensor302is in the ON state or the OFF state. If the CPU41determines here that the trailing edge limiting member position sensor302is in the OFF state, the process advances to step S203. If the CPU41determines here that the trailing edge limiting member position sensor302is in the ON state, the process advances to step S204. In step S203, the CPU41turns on the LED400and notifies the user that the plain paper mode is set. A lighting pattern at this time is predetermined, and the user can identify that the plain paper mode is set in accordance with the notification by the LED400. The process advances to step S204when the user moves the trailing edge limiting member87from the left side to the right side of the alternate long and short dashed line as shown inFIGS. 4A and 4B, and the CPU41detects that the trailing edge limiting member position sensor302is in the ON state.

In step S204, the CPU41checks the combination of sensing results from the extension lifter HP sensor303and main lifter position sensor304. When both the extension lifter HP sensor303and the main lifter position sensor304are OFF, the process advances to step S210. In this case, both the main lifter61aand the extension lifter61bare located above the extension lifter HP sensor303and the main lifter position sensor304. In this case, in step S210, the CPU41moves the main lifter61ato a standby position in the elongated paper mode as shown inFIG. 3B. After step S210, the process advances to step S211.

If the combination of the sensing results is a combination other than the above-described combination, the process advances to step S205. In this case, for example, plain paper sheets are stacked, and the main lifter61ais located below the main lifter position sensor304. In that state, a situation where the plain paper sheets remain is obtained. Therefore, in step S205, the CPU41displays, on the operation panel40, a message “As preparation for setting elongated paper sheets, remove sheets and close the storage. When using plain paper sheets, check the position of the trailing edge limiting plate.”

When the user removes sheets and closes the large-capacity deck storage62after displaying the message, in step S206, the CPU41detects that the large-capacity deck storage62is closed. In step S207, the CPU41moves the main lifter61ato the standby position in the elongated paper mode as shown inFIG. 3B. After step S207, when the CPU41detects in step S208that the user presses the storage opening/closing button306, the CPU41sets the large-capacity deck storage62in the open state in step S209. After step S209, the process advances to step S211.

In step S211, when the user sets elongated paper sheets, the CPU41detects that the elongated paper sheets are set. Then, when the user closes the large-capacity deck storage62, in step S212, the CPU41detects that the large-capacity deck storage62in the closed state. Subsequently, a feeding operation in the elongated paper mode is started.

The partition plate350and a cassette heater351will be described below. A recent feeding apparatus needs to support various paper types and needs a heat source (heating source) such as a cassette heater as measures against paper having a high friction coefficient among pieces of paper such as coated paper in particular.

FIG. 12is a flowchart showing control processing of the cassette heater351according to this embodiment. Each process inFIG. 12is implemented by, for example, the CPU41by reading out a program stored in the ROM and executing the program. When the image forming apparatus900and the paper deck3000are powered on, the processing inFIG. 12is started.

In step S301, the CPU41obtains paper-type information accepted by a user input from the image forming apparatus900. In step S302, based on the paper-type information obtained in step S301, the CPU41determines whether heating by the cassette heater351is needed. For example, if the type of paper which is comparatively thick such as coated paper is used, the CPU41determines that heating by the cassette heater351is needed.

If the CPU41determines in step S302that heating is needed, in step S303, the CPU41sets a set temperature according to a paper type which is indicated by the information obtained in step S301. Then, in step S304, the CPU41starts heating by the cassette heater351at the set temperature. On the other hand, if the CPU41determines in step S302that heating is not needed, the processing inFIG. 12ends without performing heating by the cassette heater351.

The heat source is generally installed so as to mainly warm the side of regular-size paper sheets which are used frequently. Therefore, a positional relationship among the cassette heater351, main lifter61a, extension lifter61b, and partition plate350is as shown inFIG. 9.

As shown inFIG. 9, the partition plate350is provided below the extension lifter61b, so as to partition a region below where the extension lifter61bis supported and a region where regular-size paper sheets are stacked. That is, in a state in which the main lifter61aexists below the extension lifter61b, the partition plate350is provided so as to partition the region of the main lifter61awhere the regular-size paper sheets are stacked and the region below where the extension lifter61bis supported. Moreover, the partition plate350includes opening portions502for allowing the trailing edge limiting member87to move in the conveyance direction, and opening portions501each for connecting a space in a lower portion of the main lifter61aand a space in a lower portion of the extension lifter61b. Each opening portion501for connecting (communicating) the spaces is formed to have a size through which at least a first of an adult male can pass. Furthermore, at least two opening portions501are provided to sandwich the opening portions502in a sheet width direction, as shown inFIG. 9. The total of opening areas of the opening portions501is set to be larger than opening areas out of opening areas of the opening portions502when the trailing edge limiting member87is removed on a surface perpendicular to a sheet conveyance direction.

FIG. 10is a view showing a state when regular-size paper sheets are stacked. When the regular-size paper sheets are stacked, because the paper sheets are stacked so as to block the opening portions501of the partition plate350, heat generated from the cassette heater351remains on a side where the paper sheets are stacked without flowing through the space in the lower portion of the extension lifter61b. When the main lifter61ais located in a lowermost portion, the opening areas of the opening portions501are minimized (blocked). In a range where the main lifter61amoves together with the extension lifter61b, the opening areas of the opening portions501are maximized. Between the above-described two positions of the main lifter61a, at least a part of each opening portion501is covered with the stacked sheets.

FIG. 11is a view showing a state when elongated-size paper sheets are stacked. When the elongated-size paper sheets are stacked, the paper sheets do not block the opening portions of the partition plate350, allowing heat to diffuse and rise to the side of the extension lifter via the opening portions501of the partition plate350, and warm the region of the extension lifter61bwhere the paper sheets are stacked.

Each opening portion501of the partition plate350is formed to have the size through which at least the first of an adult male can pass, allowing the user to remove a foreign substance that exists in the space below the extension lifter61bby inserting his/her hand from the opening portion. Moreover, the partition plate350has a function of preventing collapse of regular-size paper sheets. Furthermore, the partition plate350has a function of supporting the extension lifter61bin a state in which the extension lifter61bis not coupled with the main lifter61a.

As described above, according to this embodiment, by providing the partition plate350with the opening portions501each having the size through which at least the first of an adult male can pass, it is possible to supply heat of a cassette heater efficiently regardless of whether regular-size paper sheets or elongated-size paper sheets are stacked. In addition, the user can remove the foreign substance that exists in the space below the extension lifter61b.

In the above-described embodiment, the image forming system is formed by attaching the sheet feeding apparatus30to the image forming apparatus900as a discrete unit. However, the present invention is also applicable to a mode in which the image forming apparatus is formed by attaching the sheet feeding apparatus30to the image forming apparatus900integrally.

In the above-described embodiment, the arrangement using the cassette heater351has been described. That is, in the above-described embodiment, the cassette heater351is arranged for the purpose of generating an air flow in order to keep air permeability satisfactorily between the space in the lower portion of the main lifter61aand the space in the lower portion of the extension lifter61b. However, another arrangement may be provided in order to generate an air flow. For example, an arrangement that arranges a fan on an apparatus wall surface in the lower portion of the main lifter61ato generate an air flow inside may be adopted. Alternatively, an arrangement that generates an air flow between the space in the lower portion of the main lifter61aand the space in the lower portion of the extension lifter61bby combining the cassette heater351and the fan may be adopted.

This application claims the benefit of Japanese Patent Applications No. 2017-167641, filed Aug. 31, 2017, and No. 2018-150627, filed Aug. 9, 2018, which are hereby incorporated by reference herein in their entirety.