SHEET STACKING APPARATUS

Abstract

A sheet stacking apparatus includes a stacking unit, a regulating member, and a detection device. The stacking unit has a stacking surface on which sheets to be fed in a sheet-feeding direction are stacked. The regulating member is movable in the sheet-feeding direction and configured to regulate the sheet by coming into contact with an upstream edge of the sheet in the sheet-feeding direction on the stacking surface. The detection device is configured to detect a size of the sheet on the stacking surface. The detection device includes a rotatable member configured to rotate about an axis in response to movement of the regulating member, the axis extending parallel to the sheet-feeding direction as viewed from above and being positioned below the stacking surface. The detection device also includes a sensor configured to detect a position of the rotatable member.

Description

BACKGROUND

Field

The present disclosure relates to a sheet stacking apparatus in which sheets are stacked.

Description of the Related Art

Japanese Patent Laid-Open No. 2003-81446 discloses a sheet stacking apparatus that accommodates sheets to be used in image forming. In this sheet stacking apparatus, a trailing-edge regulating member regulates the position of the trailing edges of the sheets. A sensor is provided to detect the bottom portion of the trailing-edge regulating member. The length of the sheets is determined in accordance with the position of the trailing-edge regulating member that has been detected by the sensor.

In the configuration in which the sensor detects the bottom portion of the trailing-edge regulating member, when a single sensor is employed to detect the trailing-edge regulating member, the movable range of the trailing-edge regulating member is limited to the length of the bottom portion. This limit, for example, the range of sheet sizes that the sheet stacking apparatus can handle.

SUMMARY

According to some embodiments, a sheet stacking apparatus includes i) a stacking unit having a stacking surface on which sheets to be fed in a sheet-feeding direction are stacked, ii) a regulating member being movable in the sheet-feeding direction and configured to regulate the sheet by coming into contact with an upstream edge of the sheet in the sheet-feeding direction on the stacking surface, and iii) a detection device configured to detect a size of the sheet on the stacking surface. The detection device includes a rotatable member configured to rotate about an axis in response to movement of the regulating member, the axis extending parallel to the sheet-feeding direction as viewed from above and being positioned below the stacking surface. The detection device also includes a sensor configured to detect a position of the rotatable member.

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

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an inkjet recording apparatus according to an embodiment of the present disclosure.

FIGS. 2A and 2B are schematic views illustrating an internal structure of a container.

FIG. 3 is a view illustrating a relationship among the sizes of typical standard-sized sheets in a width direction and in a sheet-feeding direction.

FIG. 4 is a view illustrating a first comparative example.

FIG. 5 is a view illustrating the first comparative example.

FIG. 6 is a view illustrating the first comparative example.

FIG. 7 is a view illustrating a second comparative example.

FIG. 8 is a view illustrating the second comparative example.

FIG. 9 is a view illustrating the second comparative example.

FIG. 10 is a schematic view illustrating a structural relationship between a trailing-edge guide and a size-detection device according to the embodiment of the present disclosure.

FIG. 11 is a schematic view illustrating the structural relationship between the trailing-edge guide and the size-detection device according to the embodiment of the present disclosure.

FIG. 12 is a schematic view illustrating the structural relationship between the trailing-edge guide and the size-detection device according to the embodiment of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail with reference to the drawings, while a preferred embodiment is taken as an example. Note that as the preferred embodiment, the embodiment described herein includes technically preferable limitations. The following description of the embodiment is not intended to limit the scope of the present disclosure. Note that the features described in the embodiment are not necessarily indispensable to the present disclosure.

An inkjet recording apparatus 1 according to an embodiment of the present disclosure will be described with reference to the drawings.

FIG. 1 is a diagram schematically illustrating an example of the inkjet recording apparatus 1, which serves as an image forming apparatus. The inkjet recording apparatus 1 is a sheet-fed-type inkjet recording apparatus that uses two types of liquids such as ink and liquid agent to form ink images on sheets S and thereby produces recorded products.

The inkjet recording apparatus 1 of the present embodiment includes a sheet-feeding module 1000, a print module 2000, a drying module 3000, a fixing module 4000, and a cooling module 5000. The inkjet recording apparatus 1 also includes a reversing module 6000 and a discharged-sheet stacking module 7000.

A sheet S, which is a sheet of paper, is fed by the sheet-feeding module 1000. The sheet S is conveyed along a conveyance path to multiple processing modules and finally discharged into the discharged-sheet stacking module 7000.

The sheet-feeding module 1000, which is a sheet stacking apparatus, includes three containers 1100a to 1100c that accommodate sheets S. The containers 1100a to 1100c can be pulled out at the front side of the apparatus. The main body of the sheet-feeding module 1000 supports the containers 1100a to 1100c so as to enable the containers 1100a to 1100c to be pulled out. Sheets S stored in the containers 1100a to 1100c are picked up one by one by a separator belt 3001 and a conveyance roller, which constitute a feeder unit, and are fed to the print module 2000 in the sheet-feeding direction. The number of the containers is not limited to three (i.e., containers 1100a to 1100c) but may be one or two or four or more.

The print module 2000 includes a position correction unit (not illustrated), a print belt unit 2200, and a recording unit 2300. The sheet S sent from the sheet-feeding module 1000 is further conveyed to the print belt unit 2200 while the position of the sheet S is adjusted by the position correction unit. The recording unit 2300 is disposed so as to oppose the print belt unit 2200 with the conveyance path being interposed therebetween. The recording unit 2300 is a sheet processing unit in which a recording head positioned above the sheet S performs printing to form an image on the sheet S.

The print belt unit 2200 adsorbs the sheet S during the conveyance of the sheet S, thereby creating a clearance between the sheet S and the recording head. The multiple recording heads are arrayed in the conveyance direction. In the present example, the recording unit 2300 includes five line-type recording heads corresponding to yellow ink (Y), magenta ink (M), cyan ink (C), black ink (BK), and a liquid agent. The number of colors is not limited to the above, and the number of the recording heads is not limited to five. Ink jetting may be based on any system, for example, using thermal elements, piezoelectric elements, electrostatic elements, or MEMS elements. The inks of different colors are supplied to the recording heads from respective ink tanks (not illustrated) through ink tubes. The sheet S on which printing is performed in the recording unit 2300 is conveyed to the drying module 3000.

The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, and a warm air blower unit 3400. The drying module 3000 improves ink fixation to the sheet S by reducing the liquid content of the ink discharged onto the sheet S in the recording unit 2300.

The sheet S on which printing is performed in the recording unit 2300 of the print module 2000 is conveyed to the decoupling unit 3200 disposed in the drying module 3000. In the decoupling unit 3200, air is blown onto the sheet S to increase friction between the sheet S and the belt. The decoupling unit 3200 conveys the sheet S while holding the sheet S lightly, thereby preventing the sheet S from being displaced on the print belt unit 2200 during ink-image formation.

The sheet S conveyed from the decoupling unit 3200 is adsorbed onto, and conveyed by, the drying belt unit 3300, while the warm air blower unit 3400 disposed above the belt blows warm air onto the sheet S to dry the ink-applied surface. Drying may be performed by using warm air or by irradiating the sheet S with electromagnetic waves (such as ultraviolet rays or infrared rays) or by heat conduction and transfer from a heat source or by combined use of these methods.

The fixing module 4000 includes a fixing belt unit 4100. The fixing module 4000 fixes ink onto the sheet S conveyed from the drying module 3000 while the sheet S passes between a heated upper and lower belt units.

The cooling module 5000 includes multiple cooling units 5001 that cool the heated sheet S conveyed from the fixing module 4000. In each cooling unit 5001, air is taken into a cooling box by a fan and a pressurized air in the cooling box is discharged onto the sheet S from a nozzle disposed along a conveyance guide to cool the sheet S. The cooling units 5001 are disposed so as to interpose the conveyance path therebetween to cool both sides of the sheet S. The cooling module 5000 includes a conveyance path switcher that can switch between a conveyance path on which the sheet S is conveyed to the reversing module 6000 and a conveyance path for double-sided printing.

In the double-sided printing, the sheet S is conveyed along a conveyance path below the cooling module 5000 and passes through the fixing module 4000, the drying module 3000, and the print module 2000. The sheet S is further conveyed from the print module 2000 to a double-sided printing conveyance path in the sheet-feeding module 1000, and subsequently the print module 2000 performs printing again on the sheet S. The double-sided printing conveyance unit in the fixing module 4000 includes a reversing unit 4200 that can reverse the front and back sides of the sheet S.

The reversing module 6000 also can reverse the front side and back side of the sheet S, thereby changing the orientation of the sheet S to be discharged as desired.

The discharged-sheet stacking module 7000 includes a top tray 7200 and a discharged-sheet stacking unit 7500. The sheet S conveyed from the reversing module 6000 is arranged and stacked in the discharged-sheet stacking module 7000.

Next, the sheet-feeding module 1000 and the containers 1100a to 1100c will be described in terms of their structures and mechanisms. The containers 1100a to 1100c for storing sheets S are accommodated in the sheet-feeding module 1000. Note that the following description focuses on the container 1100a and its peripheral components because the containers 1100a to 1100c have the same structure in the present embodiment. In the present disclosure, however, the containers 1100a to 1100c do not need to have the same structure, and the containers 1100a to 1100c may be configured to store sheets having different maximum and minimum sizes. The containers 1100a to 1100c may have different detection structures or may use different detection conditions in detecting the sizes of sheets.

FIGS. 2A and 2B are schematic views illustrating an internal structure of the container 1100a. In FIG. 2A, peripheral components, such as a cover, are omitted in an aim to facilitate clear understanding. In FIG. 2B, a container frame 1110 is omitted to expose the internal structure.

The container 1100a includes a container frame 1110 and a lifter plate 1140. The container frame 1110 includes side walls of the container 1100a, and the lifter plate 1140 can ascend and descent with sheets being stacked thereon. The container 1100a also includes a pair of side guides 1121 and 1122. The side guides 1121 and 1122 can move in a sheet width direction 82 relative to the container frame 1110. When the sheets are accommodated in the container 1100a, in other words, placed on the lifter plate 1140, the side guides 1121 and 1122 come into contact with edges of the sheets, the edges being opposite in the sheet width direction 82. In other words, the side guides 1121 and 1122 are guides for regulating the position of sheets S in the sheet width direction 82. The sheet width direction 82 is the direction orthogonally intersecting a sheet-feeding direction 81. The container 1100a also includes an operation device 1125 that a user manipulates when the user moves side guides 1121 and 1122. The container 1100a also includes a trailing-edge guide 1130, which serves as a regulating member to regulate the position of the trailing edges of the sheets. The sheets are placed on a stacking surface of the lifter plate 1140, which serves as a stacking unit. In this state, the trailing-edge guide 1130 is in contact with the upstream end of each sheet in the sheet-feeding direction 81. Note that the upstream end of the sheet is otherwise called the trailing edge of the sheet. The trailing-edge guide 1130 is a guide for regulating the position of the sheet S in the sheet-feeding direction 81. The trailing-edge guide 1130 is supported by the container frame 1110 so as to be able to move in a predetermined movement direction. Note that as viewed at least from above, the movement direction of the trailing-edge guide 1130 is parallel to the sheet-feeding direction in the present embodiment.

The container 1100a includes an abutting portion 2001. When sheets are placed on the lifter plate 1140, the downstream end of each sheet in the sheet-feeding direction 81 comes into contact with the abutting portion 2001. The downstream end of each sheet is otherwise called the leading edge of the sheet.

A rotary sensor (not illustrated) detects the positions of respective side guides 1121 and 1122. Accordingly, the size of the sheet S in the width direction can be detected in a stepless manner.

Referring to FIGS. 10 to 12, the following describes the trailing-edge guide 1130 of the present embodiment and a structure for detecting the position of the trailing-edge guide 1130. Note that for convenience of explanation, FIGS. 10 to 12 omit part of the container frame 1110 and also omit the lifter plate 1140 on which the sheets S are stacked.

As illustrated in FIG. 10, a size-detection device 1150 configured to detect the position of the trailing-edge guide 1130 is disposed at the bottom of the container frame 1110 at a position more upstream of the side guides 1121 and 1122 in the sheet-feeding direction 81. FIGS. 11 and 12 are schematic illustrations focusing on the size-detection device 1150.

The size-detection device 1150 includes a detection lever 1151 and a photo sensor 1152. The detection lever 1151 serves as a rotatable member. The photo sensor 1152 generates a signal corresponding to a position of the detection lever 1151. The detection lever 1151 is rotatably supported by a rotation shaft 71. The detection lever 1151 is rotatable about the rotation axis extending parallel to the sheet-feeding direction as viewed from above. The detection lever 1151 can be switched between a first state in which the detection lever 1151 is in contact with a bottom portion 1130a of the trailing-edge guide 1130 as illustrated in FIG. 11 and a second state in which the detection lever 1151 is not in contact with the bottom portion 1130a as illustrated in FIG. 12. The photo sensor 1152 is configured to detect the position of the detection lever 1151. The photo sensor 1152 determines whether the detection lever 1151 is in the first state or in the second state.

The detection lever 1151 includes a guide contact portion 1151a and a sensor flag portion 1151b. The guide contact portion 1151a comes into contact with the trailing-edge guide 1130, and the sensor flag portion 1151b is positioned opposite to the guide contact portion 1151a with the rotation shaft 71 being interposed therebetween. The guide contact portion 1151a is elongated in the sheet-feeding direction 81. The guide contact portion 1151a has a tapered portion 1151c at the downstream end of the guide contact portion 1151a in the sheet-feeding direction 81. The tapered portion 1151c is a portion bent downward.

When the trailing-edge guide 1130 is positioned in a predetermined range, the trailing-edge guide 1130 presses the guide contact portion 1151a down. When the guide contact portion 1151a is pressed down, the sensor flag portion 1151b at the opposite side moves upward. The above-described first state is a state in which the guide contact portion 1151a is pressed down by the bottom portion 1130a of the trailing-edge guide 1130 and the sensor flag portion 1151b is raised as illustrated in FIG. 11 (in other words, the detection lever 1151 is at the first position). When the detection lever 1151 is in the first state, the photo sensor 1152 is in the state of “OFF”, in other words, the photo sensor 1152 outputs an “OFF” signal. In other words, in the first state, the sensor flag portion 1151b of the detection lever 1151 does not block the optical path of the photo sensor 1152.

The detection lever 1151 is shaped such that the sensor flag portion 1151b is heavier than the guide contact portion 1151a, in other words, a larger weight moment acts on the sensor flag portion 1151b. Accordingly, when the trailing-edge guide 1130 is not in contact with the detection lever 1151 as illustrated in FIG. 12, the guide contact portion 1151a ascends and the sensor flag portion 1151b descends, thereby causing the detection lever 1151 to be in the second state (in other words, the detection lever 1151 is at the second position). Put another way, when the trailing-edge guide 1130 is moved and the bottom portion 1130a is separated from the detection lever 1151, the detection lever 1151 rotates by its own weight to the position in the second state. When the detection lever 1151 is in the second state, the photo sensor 1152 is in the state of “ON”, in other words, the photo sensor 1152 outputs an “ON” signal. In other words, in the second state, the sensor flag portion 1151b of the detection lever 1151 blocks the optical path of the photo sensor 1152.

In the present embodiment, the first state corresponds to large size of sheet, and the second state corresponds to small size of sheet. When the trailing-edge guide 1130 passes a predetermined boundary position between the large size and the small size, the contact state between the detection lever 1151 and the trailing-edge guide 1130 is switched. A control unit 3002 (see FIG. 1) reads the signal from the photo sensor 1152 and determines whether the sheet is small or large.

In the present embodiment, the photo sensor 1152 (see FIGS. 11 and 12) is employed to determine the size of sheets in the sheet-feeding direction 81 when the sheets are placed in the container 1100a. The larger size and the smaller size are determined by comparing the size of the sheets with a predetermined threshold. FIG. 3 illustrates a relationship among the sizes of typical standard-sized sheets in the width direction and in the sheet-feeding direction. The sheet-feeding module 1000 is able to handle these sizes of the typical standard-sized sheets. As can be seen from FIG. 3, some standard-sized sheets have the same size in the sheet width direction 82 but have different sizes in the sheet-feeding direction 81. In these combinations of sheets, the maximum number of size differences in the sheet-feeding direction 81 is two. Accordingly, if the size of the sheet accommodated in the container 1100a can be determined to be larger or smaller in the sheet-feeding direction 81, the type of the sheet size can be determined.

In order to reduce the cost, a single sensor (i.e., a single photo sensor 1152) is employed to detect the size of the sheets in the sheet-feeding direction 81. In other words, for the purpose of cost reduction, a common threshold is set up to differentiate the small-size sheets from the large-size sheets in the sheet-feeding direction 81 in order to differentiate the standard-sized sheets having the same size in the sheet width direction 82. In this case, the threshold that can be set ranges between the maximum one of the small-size sheets and the minimum one of the large-size sheets in the sheet-feeding direction among all the possible combinations of the sheets that have the same size in the sheet width direction and have different sizes (i.e., small and large) in the sheet-feeding direction. Put another way, the standard-sized sheets that the sheet-feeding module 1000 can handle include multiple pairs of short and long sheets, in the sheet-feeding direction, of which the width is the same. Among these multiple pairs, a first pair is defined as a pair that includes the shortest one among the long sheets of the pairs. In addition, a second pair is defined as a pair that includes the longest one among the short sheets of the pairs. In addition, an upper limit position is defined as the position at which the trailing-edge guide 1130 regulates the long sheet of the first pair, and a lower limit position is defined as the position at which the trailing-edge guide 1130 regulates the short sheet of the second pair. Accordingly, the size-detection device 1150 is configured such that the output of the photo sensor 1152 is changed while the trailing-edge guide 1130 moves between the upper limit position and the lower limit position. In the example of FIG. 3, the first pair corresponds to the pair of G-LGL and G-LTRR sheets. The second pair corresponds to the pair of LGL and LTRR sheets.

In the case of standard-sized sheets illustrated in FIG. 3, the lower limit position is that of the LTRR sheet with a width of 215.9 mm and a length of 279.4 mm in the sheet-feeding direction. The upper limit position is that of the G-LGL sheet with a width of 203.2 mm and a length of 330.2 mm in the sheet-feeding direction. Accordingly, the threshold for differentiating the short sheet from the long sheet in the sheet-feeding direction is set in a range from 279.4 mm to 330.2 mm, which can differentiate all the types of standard-sized sheets that the sheet-feeding module 100 can handle. Note that these values are to be used for the standard-sized sheets listed in FIG. 3 by way of example. Other values may be used for other combinations of standard-sized sheets that are different from those illustrated in FIG. 3. For example, if the standard-sized sheets do not include G-LTRR and G-LGL sheets, the threshold is set in a range from 279.4 mm to 355.6 mm to differentiate LTRR and LGL sheets from each other. In the case of size detection errors in the sheet width direction 82 being taken into account, the threshold may be set so as to differentiate the A4R sheet having a length of 297 mm in the sheet-feeding direction from other sheets in the vicinity. In the present embodiment, the difference between the maximum size and the minimum size in the sheet-feeding direction, which can be handled by the sheet-feeding module 1000, is greater than the threshold. The threshold here is the distance between the abutting portion 2001 with which the leading edge of the sheet comes into contact and the position of the trailing-edge guide 1130 at which the output of the photo sensor 1152 changes.

In general, many sheet stacking apparatuses are equipped with a mechanism to detect the positions of regulation guides that regulate the edges of sheets in the width direction and also regulate the trailing edges of sheets in the sheet-feeding direction in order to determine the size of the sheets stacked therein. For example, in determining the sheet size, a rotary sensor is used to steplessly detect the size in the width direction. To detect the size in the sheet-feeding direction, many sheet stacking apparatuses are equipped with one photo sensor or two to determine whether the size is large or small with respect to a predetermined threshold. For example, when a sheet having a width of 297 mm is detected, the sheet is either an A4-size sheet having a length of 210 mm in the sheet-feeding direction or an A3-size sheet having a length of 420 mm. Accordingly, the sheet size can be determined by detecting the length in the sheet-feeding direction. Note that the size determination assumes that the standard-sized sheets are stacked.

First Comparative Example

A structure of a first comparative example illustrated in FIGS. 4 to 6 is conceivable as a method of detecting the size of sheet in the sheet-feeding direction. In this structure, a sensor flag 1131 elongated in the sheet-feeding direction is attached to the trailing-edge guide 1130, and a sensor 1132 for detecting the sensor flag 1131 is disposed at the bottom of the container frame 1110. In FIGS. 4 to 6, L1 denotes the smallest sheet size that the container 1100a can handle in the sheet-feeding direction, L2 denotes the threshold for differentiating between small size and large size, and L3 denotes the largest sheet size in the sheet-feeding direction. FIGS. 4 to 6 illustrates the states of the container 1100a in which the trailing-edge guide 1130 is at respective positions corresponding to L1 to L3. The sensor flag 1131 is elongated in the sheet-feeding direction so as to match both minimum and maximum sizes of the sheets S. The sensor flag 1131 needs to stay between the walls of the container 1100a. Accordingly, when the length of the sensor flag 1131 is denoted by reference sign f, the relationship of L1, L2, and L3 can be expressed in the following formulae:

$L1>f$ $f>L3-L2$ $L1>L3-L2$ $L2>L3-L1$

When the above conditions are satisfied, the structure of the first comparative example can be implemented using the minimum number of components. A problem, however, is that the range of sizes that this structure can handle in the sheet-feeding direction, which is expressed by L3-L1, cannot exceed the threshold of L2. For example, in the case where the minimum size L1 is 266.7 mm of the G-LTRR size sheet having a width of 203.2 mm and the threshold L2 is 330.2 mm, which is the largest in the above range, the maximum size L3 is preferably less than or equal to 596.9 mm.

In other words, in the first comparative example illustrated in FIGS. 4 to 6, the threshold setting for size detection is restricted depending on the sizes that the sheet-feeding module can handle. On the other hand, in the present embodiment, the threshold for size detection can be set without being restricted as is the case for the structure of the first comparative example (illustrated in FIGS. 4 to 6).

Second Comparative Example

As described above, the first comparative example has the problem that the threshold for size detection is restricted depending on the sheet sizes that the container can handle. In order to solve this problem, the structure of the second comparative example illustrated in FIGS. 7 to 9 is conceivable. In the second comparative example, as illustrated in FIG. 7, the sensor flag 1131 elongated in the sheet-feeding direction is disposed at the container frame 1110 so as to be able to rotate about a shaft extending in the sheet width direction.

In other words, the sensor flag 1131 rotates about an axis extending in the sheet width direction. In the second comparative example illustrated in FIGS. 7 to 9, an urging member 1133 is provided to cause the sensor flag 1131 to return from a first state to a second state.

FIG. 7 illustrates a state in which the trailing-edge guide 1130 stays on the small-size side and is not in contact with the sensor flag 1131. FIGS. 8 and 9 illustrate a state in which the trailing-edge guide 1130 stays on the large-size side and is in contact with the sensor flag 1131. When the trailing-edge guide 1130 returns from the large-size side to the small-size side, the urging member 1133 causes the sensor flag 1131 to return to the position corresponding to the small size.

The size of sheet in the sheet-feeding direction can be determined based on the signal from the sensor 1132 that detects the position of the sensor flag 1131.

In the structure of the second comparative example, even when the size of the sheet that the container frame 1110 can handle increases in the sheet-feeding direction, it is sufficient to simply increase the length of the sensor flag 1131 attached to the bottom of the container frame 1110. Accordingly, the structure of the second comparative example can handle a wider range of sheet sizes in the sheet-feeding direction compared with the structure of the first comparative example illustrated in FIG. 4 without being restricted by the threshold constraints although the number of components somewhat increases.

In the second comparative example, however, it is preferable to apply a force to the sensor flag 1131 so as to match the urging member 1133 when the trailing-edge guide 1130 is moved from the small-size side to the large-size side as illustrated in FIG. 8. In this case, the trailing-edge guide 1130 applies the force to the sensor flag 1131 at a position near the rotation shaft. Accordingly, this structure with the small radius of the moment of rotation may impose a large burden on a user. It is possible to increase the radius of the moment of rotation by disposing the rotation shaft near the leading edge of the sheets. In this case, however, it is preferable to increase the length of the sensor flag 1131 and the urging power of the urging member 1133, which leads to an increase in the size of the structure.

The present embodiment, however, is different from the second comparative example in that the detection lever 1151 can swing by gravity, which leads to cost reduction compared with the structure of the second comparative example (illustrated in FIGS. 7 to 9) that uses the urging member 1133. In addition, the distance between the rotation shaft of the detection lever 1151 and the contact position with which the trailing-edge guide 1130 comes into contact does not vary in the present embodiment, which alleviates the burden on a user when switching the contact state.

Accordingly, in the present embodiment, the sheet stacking apparatus can handle a wider range of sheet sizes in the sheet-feeding direction, and the size detection in the sheet-feeding direction can be implemented with a small number of components, in other words, at a lower cost.

In the above embodiment, the image forming apparatus equipped with the inkjet-type image forming unit has been described by way of example. The image forming apparatus, however, may be an apparatus equipped with an image forming unit that employs the electrophotographic process.

According to the embodiment described above, the sheet stacking apparatus can detect a wide range of sizes of standard-sized sheets stacked at the position regulated by the regulating members.

While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of priority from Japanese Patent Application No. 2023-168811 filed Sep. 28, 2023, which is hereby incorporated by reference herein in its entirety.

Claims

1. A sheet stacking apparatus, comprising: a stacking unit having a stacking surface on which sheets to be fed in a sheet-feeding direction are stacked;a regulating member being movable in the sheet-feeding direction and configured to regulate the sheet by coming into contact with an upstream edge of the sheet in the sheet-feeding direction on the stacking surface; anda detection device configured to detect a size of the sheet on the stacking surface,wherein the detection device includes a rotatable member configured to rotate about an axis in response to movement of the regulating member, the axis extending parallel to the sheet-feeding direction as viewed from above and being positioned below the stacking surface, anda sensor configured to detect a position of the rotatable member.

2. The sheet stacking apparatus according to claim 1, wherein the sensor is configured to output different signals between when the rotatable member is at a first position at which the regulating member is in contact with the rotatable member and when the rotatable member is at a second position at which the regulating member is separated from the rotatable member.

3. The sheet stacking apparatus according to claim 2, wherein the rotatable member rotates by gravity from the first position to the second position in response to the regulating member being separated from the rotatable member.

4. The sheet stacking apparatus according to claim 1, further comprising: a feeder unit configured to feed the sheet on the stacking surface in the sheet-feeding direction.

5. The sheet stacking apparatus according to claim 4, wherein among multiple pairs of a long sheet and a short sheet with respect to the sheet-feeding direction, the long sheet and the short sheet being equal-width standard-sized sheets that the sheet stacking apparatus can handle, a first pair is defined as a pair including a shortest one among the long sheets of the multiple pairs, and a second pair is defined as a pair including a longest one among the short sheets of the multiple pairs, andwherein the sensor of the detection device changes output when the regulating member moves between a position at which the regulating member regulates the long sheet of the first pair and a position at which the regulating member regulates the short sheet of the second pair.

6. The sheet stacking apparatus according to claim 1, further comprising: an abutting portion with which a leading edge of the sheet in the sheet-feeding direction comes into contact when the sheet is on the stacking surface,wherein the regulating member regulates a position of a trailing edge of the sheet in the sheet-feeding direction, andwherein a difference between maximum and minimum sizes, in the sheet-feeding direction, that the sheet stacking apparatus can handle is greater than a distance between the abutting portion and a position of the regulating member at which the output of the sensor changes in response to movement of the regulating member.

7. The sheet stacking apparatus according to claim 1, further comprising: an abutting portion with which a leading edge of the sheet in the sheet-feeding direction comes into contact when the sheet is on the stacking unit,wherein the regulating member regulates a position of a trailing edge of the sheet in the sheet-feeding direction, andwherein a distance between the abutting portion and a position of the regulating member at which the output of the sensor changes in response to movement of the regulating member is 279.4 mm or more and 355.6 mm or less.

8. The sheet stacking apparatus according to claim 1, wherein the regulating member is configured to press the rotatable member to cause the rotatable member to rotate, andwherein the regulating member comes into contact with the rotatable member at a position below the stacking surface.

9. The sheet stacking apparatus according to claim 1, further comprising: an apparatus body; anda container movably supported by the apparatus body,wherein the stacking unit, the regulating member, and the detection device are disposed in the container.

10. An image forming apparatus, comprising: the sheet stacking apparatus according to claim 1; andan image forming unit configured to form an image on the sheet fed from the sheet stacking apparatus.