Sheet material stacking device and image forming apparatus having same

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet material stacking device, and more particularly, it relates to a sheet material stacking device having a function for stacking sheet materials on a stacking tray and applicable to an image forming apparatus such as a copying machine, a printer, a facsimile and the like.

2. Related Background Art

In conventional image forming apparatuses such as copying machines, printers, facsimiles and the like, there is provided a stacking tray on which sheet materials discharged from a main body of the image forming apparatus are stacked, and an example of such an image forming apparatus is shown in FIG.

6

. In

FIG. 6

, the reference numeral

201

denotes a main body of the image forming apparatus;

210

denotes a sheet material stacking device; and

222

,

251

,

252

,

253

,

254

and

255

denote stacking trays on which sheet materials discharged and sorted from the sheet material stacking tray

210

are stacked. In order to minimize the installation space of the system, the stacking trays

251

to

255

include extensible/retractable extension trays

261

to

265

, respectively.

However, the above-mentioned conventional example has the following problems.

That is to say, thicknesses of the stacking trays

251

to

255

must be increased to hold the extension trays

261

to

265

therein. More particularly, the thickness of each stacking tray is required to be not less than 12 mm.

Particularly when the number of the stacking trays is increased, the total height of the apparatus will be increased accordingly. To avoid this, there has been proposed a technique in which each of extension trays

361

is disposed at one side (upper side) of each of the stacking trays

351

,

352

, as shown in FIG.

7

. However, with this arrangement, a leading end of a sheet material

300

discharged from a main body

210

by a pair of rollers

353

of an image forming apparatus may be caught by an upstream end

361

a

of the extension tray

361

.

Further, when the stacking trays are arranged conversely (i.e., the extension trays are disposed at lower sides of the stacking trays), if an upwardly curled sheet material is discharged onto the extension tray of the lower stacking tray, the leading end of the sheet material may be caught by the upstream end of the extension tray of the upper stacking tray, thereby causing the sheet jam.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a sheet material stacking device in which thicknesses of sheet material stacking means are reduced and a discharged sheet material is prevented from being caught thereby to increase stacking ability.

The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a sheet material stacking device comprising a sheet material discharging means for discharging a sheet material, a sheet material stacking means on which the sheet materials discharged by the sheet material discharging means are stacked, and an extension stacking means extensibly housed within the sheet material stacking means and capable of extending in accordance with a size of the sheet material, and wherein the extension stacking means has an inclined surface at an upstream end thereof in a sheet material stacking direction.

A further object of the present invention is to provide a sheet material stacking tray arrangement comprising a stacking tray on which sheet materials are stacked, and an extension tray extensibly held in the stacking tray, and wherein the extension tray has an inclined surface at an upstream end thereof in a sheet material stacking direction.

With the above-mentioned construction, when the sheet material is discharged by the sheet material discharging means onto the sheet material stacking means, if a size of the sheet is great, the extension stacking means is drawn from the sheet material stacking means to provide an extension tray. Since the extension stacking means has the inclined surface at its upstream end, even if a leading end of the discharged sheet material contacts with the upstream end of the extension stacking means, the leading end of the sheet material is slid on the inclined surface to be smoothly rested on the sheet material stacking means. In this way, the sheet materials can be stacked on the sheet material stacking means stably without increasing the thickness of the sheet material stacking means and with preventing the leading end of the sheet material from being caught by the extension stacking means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is an elevational sectional view of a sheet material stacking device according to the present invention;

FIG. 2

is an elevational sectional view of a sheet material stacking device according to the present invention;

FIG. 3

is a schematic elevational sectional view of an image forming apparatus to which the sheet material stacking device according to the present invention can be applied;

FIG. 4A

is a plan view showing a sheet material stacking tray portion which is a main part of the sheet material stacking device according to the present invention,

FIG. 4B

is a sectional view taken along the line

4

B—

4

B in

FIG. 4A

, and

FIG. 4C

is a sectional view taken along the line

4

C—

4

C in

FIG. 4A

;

FIG. 5A

is a plan view for explaining an operation of the sheet material stacking tray portion of

FIG. 4A

, and

FIG. 5B

is a sectional view taken along the line

5

B—

5

B in

FIG. 5A

;

FIG. 6

is a schematic side view of an image forming apparatus having a conventional sheet material stacking device; and

FIG. 7

is an elevational sectional view for explaining an operation of a sheet material stacking tray portion of the conventional sheet material stacking device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be fully explained in connection with a preferred embodiment thereof with reference to the accompanying drawings. Incidentally, in the following embodiment, a sheet material stacking device used with an image forming apparatus such as a copying machine will be described as an example.

[Construction of Image Forming Apparatus]

First of all, a schematic construction of the image forming apparatus will be briefly described with reference to FIG.

3

. As shown in

FIG. 3

, an automatic original feeding device

2

for automatically circulating originals D is rested on an upper surface of a main body of the image forming apparatus

1

. Further, a sheet material stacking device

10

having a tray

22

for discharging a sheet material in a face-up fashion and a plurality of stacking trays

51

for discharging a sheet material in a face-down fashion and the like disposed at a downstream side (left in

FIG. 3

) of the image forming apparatus.

The image forming apparatus

1

is of electrophotographic type which is well-known in the art (thus, a detailed explanation thereof will be omitted). In the image forming apparatus, an image of the original D rested on a platen glass

3

is imaged on a photosensitive drum

4

as a latent image by an optical system (not shown), and the latent image is developed by a developing device

5

as a visual image (toner image). In synchronism with this, a sheet material S is supplied to an image forming means including the photosensitive drum

4

by a feeding means such as a feeding roller. The toner image on the photosensitive drum

4

is transferred onto the sheet material S by a transferring device

6

. Then, the sheet material is sent to a fixing device

7

, where the toner image is permanently fixed to the sheet material.

The sheet materials S on which the image was formed in this way are normally stacked on the stacking tray

51

successively in a face-up (imaged surface facing upwardly) fashion by a pair of discharge rollers (discharging means)

8

. However, when the image formation is effected in a page sequence (for example, for 10 pages, from a first page to a tenth page), if the imaged sheet materials are successively stacking in the face-up fashion, the sheet materials are stacked in a sequence opposite to the page sequence. In order to stack the sheet materials in the page sequence, the sheet material stacking device

10

(described later) is mounted in the vicinity of a discharge opening

9

of the main body

1

of the image forming apparatus. By using this device, when the image formation is effected in the sequence opposite to the page sequence, the sheet materials can successively be stacked on a stacking tray

22

with the imaged surfaces facing upwardly (the face-up fashion), and, when the image formation is effected in the page sequence, the sheet materials can successively be stacked with the imaged surfaces facing downwardly (face-down fashion) while reversing a front surface and a rear surface of the sheet material to order the imaged sheet materials in the page sequence.

[Construction of Sheet Material Stacking Device]

Next, a construction of the sheet material stacking device

10

will be fully explained with reference to

FIGS. 1

to

3

.

FIGS. 1 and 2

are sectional views showing a schematic construction of the sheet material stacking device according to the present invention.

In

FIG. 3

, in order to convey the sheet material after it was fed-in and the front surface and the rear surface of the sheet material was reversed, a plurality (two in the illustrated embodiment) of rotatable conveying rollers

12

,

13

abut against an outer surface of a conveying roller

11

rotated in a given direction (shown by the arrow in FIG.

3

). The conveying roller

11

and the roller

12

abutting against the roller from the above acts as a pair of feed-in rollers for feeding-in the sheet material S, and, the conveying roller

11

and the roller

13

abutting against the roller from the below acts as a pair of feed-out rollers for feeding-out the sheet material S. That is to say, the sheet material S is fed-in by the pair of feed-in rollers

11

,

12

and is fed-out by the pair of feed-out rollers

11

,

13

.

A guide member

19

directs the sheet material S discharged from the discharge opening

9

of the image forming apparatus

1

to a nip of the pair of feed-in rollers

11

,

12

. The guide member

19

can be rocked around the conveying roller

11

in accordance with a sheet material discharging position (positions of the discharge opening and a nip of the pair of discharging rollers) of the main body

1

of the image forming apparatus. Accordingly, by rocking the guide member

19

on demand, the sheet material stacking device can accommodate various image forming apparatuses having different sheet material discharging positions.

A flapper (switching means)

14

is disposed at a downstream side of the pair of feed-in rollers

11

,

12

and can selectively be switched around a rotational center shaft

14

a by an actuator means such as a solenoid (not shown) between an upper position shown by the solid line in

FIG. 3 and a

lower position. That is to say, a plurality of conveying paths located at the downstream side of the conveying roller

11

can selectively be switched by the flapper

14

. More specifically, when the flapper

14

is switched to the solid line position (upper position) in

FIG. 3

, the sheet material S is guided into a reversing path

24

. On the other hand, when the flapper

14

is switched to the lower position, the sheet material S is guided into a discharging path

20

with the imaged surface facing upwardly (face-up condition) without reversing the front surface and the rear surface of the sheet material. Accordingly, by selectively switching the flapper

14

, the face-up stacking and the face-down stacking can be selected.

The discharging path

20

includes a pair of discharging rollers

21

for discharging the sheet material S onto a face-up discharging stacking tray

22

out of the device. The stacking tray

22

is detachably attached to the sheet material stacking device

10

, and the sheet materials S discharged by the pair of discharging rollers

21

are successively stacked on the stacking tray

22

.

A feed-back roller

16

is always rotated in a direction (shown by the arrow) opposite to that of the conveying roller

11

to feed-out the sheet material S fed-in the reversing path

24

. The feed-back roller

16

is disposed below an extension line of a tangential line of the nip of the pair of feed-in rollers

11

,

12

and nearer the pair of feed-in rollers

11

,

12

than a position to which the leading end of the sheet material S fed-in from the pair of feed-in rollers

11

,

12

reaches. Accordingly, the sheet material S guided by the flapper

14

switched to the solid line position in

FIG. 3

is fed-in the reversing path

24

without contacting with the feed-back roller

16

.

Further, a roller

15

as a driven rotary member is rotatably attached to a portion of the flapper

14

opposed to the feed-back roller

16

. Thus, when the flapper

14

is switched to the lower position, the roller

15

is urged against the feed-back roller

16

to be rotated by the rotation of the feed-back roller, and, when the flapper

14

is switched to the solid line position in

FIG. 3

, the roller

15

is spaced apart from the feed-back roller

16

.

That is to say, the sheet material S fed into the reversing path

24

by the flapper

14

switched to the solid line position in

FIG. 3

is temporarily discharged onto a reversing tray

25

through a temporary discharge opening

24

a

without contacting the leading end of the sheet material with the feed-back roller

16

. In this case, although the sheet material S is temporarily exposed out of the apparatus, since the temporary discharge opening

24

a

is located between the stacking tray

22

and the face-down discharging stacking tray

51

(described later), the sheet material S temporarily exposed out of the apparatus through the temporary discharge opening

24

a

is protected by the stacking trays

22

,

51

to prevent the user from touching the sheet material. Therefore, skew-feeding and damage of the sheet material S which may be caused by contacting the user with the sheet material can be prevented, thereby achieving the smooth reversing and conveyance of the sheet material. Further, since the sheet material S temporarily exposed is concealed by the stacking trays

22

,

51

, a neat appearance during operation is maintained.

The reversing tray

25

disposed below the temporary discharge opening

24

a

prevents the sheet material S temporarily discharged from contacting with the sheet materials S already stacked on the face-down discharging stacking tray

51

. Thus, disordering or misalignment of the sheet materials S stacked on the stacking tray

51

due to the above contact can be prevented, thereby maintaining a neat stacking condition.

Sensors (detecting means)

17

,

18

for detecting a trailing end of the sheet material S are disposed at an upstream side of the pair of feed-in rollers

11

,

12

. In the face-down discharging, when the trailing end of the sheet material S is detected by the sensors

17

,

18

, the flapper

14

is switched from the solid line position in

FIG. 3

to the lower position by the actuator means such as a solenoid in response to a detection signal from the sensors. Accordingly, a tip end of the flapper

14

is smoothly shifted from the nip of the pair of feed-in rollers

11

,

12

to a nip of the pair of feed-out rollers

11

,

13

.

The sheet material S is pushed toward the feed-back roller

16

by the switching (lowering) action of the flapper

14

. That is to say, when the flapper

14

is switched from the solid line position in

FIG. 3

to the lower position, the roller

15

of the flapper

14

abuts against the feed-back roller

16

to pinch the sheet material S between the feed-back roller

16

and the roller

15

, thereby conveying the sheet material toward the pair of feed-out rollers

11

,

13

in a direction opposite to the conveying-in direction.

The sheet material fed-out by the pair of feed-out rollers

11

,

13

is directed to one of a plurality (seven in the illustrated embodiment) of downstream discharge openings

61

to

67

, from which the sheet material is discharged onto one of the stacking trays

51

to

57

with the imaged surface facing downwardly (face-down condition). For example, when a discharged command for the uppermost stacking tray

51

is emitted, the flapper

14

is switched from the solid line position in

FIG. 3

to the lower position, and the sheet material is discharged onto the stacking tray

51

by a pair of discharging rollers

71

disposed in the vicinity of the uppermost discharge opening

61

. In this case, the sheet materials S are successively discharged with imaged surfaces facing downwardly (i.e., in the image forming sequence).

Now, a case where a plurality of sheet materials are continuously fed-in and are successively stacked on the stacking tray

51

will be explained. When the trailing end of the sheet material is detected by the sensors

17

,

18

, at a timing when the trailing end of the sheet material leaves the sensors

17

,

18

, the flapper

14

is lowered as mentioned above to direct the sheet material to the nip of the pair of feed-out rollers

11

,

13

, and the sheet material is pinched between the pair of feed-back rollers

15

,

16

to be conveyed to the pair of feed-out rollers

11

,

13

.

As shown in

FIG. 3

, the flapper

14

is designed so that the tip end of the flapper is overlapped with the conveying roller

11

in an axial direction. Accordingly, the sheet material can be conveyed effectively due to friction between the tip end of the flapper

14

and the conveying roller

11

, and the flapper

14

also act as a guide for guiding the sheet material to the pair of feed-out rollers

11

,

13

to direct the sheet material to the nip of the pair of feed-out rollers

11

,

13

smoothly. When the lowered position of the tip end of the flapper

14

is selected to become lower than the rotation center of the conveying roller

11

, the leading end (trailing end prior to the reversing of the front surface and the rear surface of the sheet material) of the sheet material is directed to the nip of the pair of feed-out rollers

11

,

13

more smoothly without abutting against the conveying roller

11

.

Explaining in more detail, the trailing end of the sheet material left the nip of the pair of feed-in rollers

11

,

12

is urged against the conveying roller

11

by the tip end of the rockable flapper

14

, and the sheet material is conveyed in the same direction by the rotational friction force of the conveying roller

11

even after the sheet material leaves the nip of the pair of feed-in rollers

11

,

12

. This conveyance continues up to a position where the friction force of the conveying roller

11

disappears, i.e., a position where the tip end of the lowered flapper

14

contacts with the conveying roller

11

with the interposition of the sheet material. When the trailing end of the sheet material leaves such a position, the flapper

14

is further lowered. When the sheet material is fed back while being pinched between the pair of feed-back rollers

15

,

16

, the trailing end of the sheet material has already ridden over the conveying roller

11

, so that the sheet material can smoothly be directed to the nip of the pair of feed-out rollers

11

,

13

.

When the tip end (trailing end prior to the reversing of the front surface and the rear surface of the sheet material) of the sheet material is pinched between the pair of feed-out rollers

11

,

13

, the flapper

14

is lifted to separate the roller

15

from the feed-back roller

16

. At this timing, a leading end of a next (succeeding) sheet material is pinched between the pair of feed-in rollers

11

,

12

and then is directed to the reversing path

24

. Accordingly, the succeeding sheet material is directed to the temporary discharge opening

24

a

along the upper surface (imaged surface) of the preceding sheet material without contacting with the feed-back roller

16

. When the trailing end (leading end prior to the reversing of the front surface and the rear surface of the sheet material) of the preceding sheet material leaves the nip of the pair of feed-out rollers

11

,

13

, the trailing end of the succeeding sheet material is detected by the sensors

17

,

18

. When the trailing end of the succeeding sheet material leaves the nip of the pair of feed-in rollers

11

,

12

, the similar reversing operation is repeated .

Therefore, the continuously fed sheet materials can surely be conveyed at a high speed while reversing the front surface and the rear surface thereof, and, thus, the sheet material stacking device particularly suitable for an image forming apparatus capable of effecting the image formation at a high speed can be provided. Since the conveying roller

11

and the feed-back roller

16

are rotated in their given directions, unlike the conventional devices, a complicated driving mechanism for reversibly rotating the rollers and a control means therefor are not required, thereby providing a less expensive device.

[Construction of Sorting Mechanism]

Next, a mechanism for sorting the sheet materials onto the stacking trays will be fully explained with reference to

FIGS. 1 and 2

. In the illustrated embodiment, as shown in

FIGS. 1 and 2

, while a sheet material stacking device having seven face-down discharging stacking trays was illustrated, the present invention is not limited to such a device, but, the number of the face-down discharging stacking trays can be suitably selected on demand.

First of all, the entire construction of the sheet material stacking device

10

will be explained with reference to

FIGS. 1 and 2

. In

FIGS. 1 and 2

, the stacking trays (sheet material stacking means)

51

to

57

comprises bins for stacking and holding the sheet materials fed out from the discharge openings

61

to

67

.

Pairs of discharging rollers (discharging means)

71

to

76

serve to feed out the sheet materials onto the associated stacking trays

51

to

56

.

A common convey path

30

serves to convey the recorded sheet materials to sorting portions (portions branched from the common convey path to the respective stacking trays) vertically and is defined by both guide members extending substantially in parallel with an overlapped direction of the stacking trays

51

to

57

.

[Explanation of Pairs of Conveying Rollers in Common Convey Path]

The common convey path

30

includes a plurality (three in the illustrated embodiment) of pairs of conveying rollers

31

to

33

equidistantly spaced apart from each other, the number of pairs being smaller than the number of flappers

81

to

86

. The sheet material is conveyed vertically (from above to below in

FIG. 1

) through the common convey path

30

by the pairs of conveying rollers

31

to

33

.

In the illustrated embodiment, the three pairs of conveying rollers

31

to

33

are disposed immediately at a downstream side of three alternate flappers (second, fourth and sixth flappers

82

,

84

,

86

which will be described later). This arrangement simplifies the construction in comparison with a case where a pair of conveying rollers are provided immediately at a downstream side of all of flappers.

The flappers

81

to

86

act as switching members to direct the sheet material to a desired one of the pairs of discharging rollers

71

to

76

. The flappers

81

to

86

have rotation centers

81

a

to

86

a

offset from the common convey path

30

toward the respective discharge openings so that each of the flappers can be rocked between a closed position (shown by the solid line in

FIG. 1

) where the common convey path

30

is not blocked by the flapper and an open position (shown by the chain double-dashed line) the common convey path

30

is blocked by the flapper.

Solenoids (actuator means)

34

,

35

(

FIG. 2

) serve to selectively rock the flappers

81

to

86

. The solenoid

34

selectively rocks alternate first, third and fifth flappers

81

,

83

,

85

and the solenoid

35

selectively rocks alternate second, fourth and sixth flappers

82

,

84

,

86

. The solenoids are mounted side by side on a lower frame (not shown) of the sheet material stacking device

10

.

With an arrangement as mentioned above, the construction of the sheet material stacking device is simplified, thereby preventing the device from becoming expensive and bulky. For example, although the plurality of flappers can be rocked by a single solenoid, in this case, control for open/close timing of the flappers becomes difficult in comparison with the illustrated embodiment.

Link members (connection means)

36

,

37

are connected to movable portions of the solenoids

34

,

35

via arm members

38

,

39

rockably attached to the frame (not shown) of the sheet material stacking device

10

so that the link members are operated integrally with the movable portions of the solenoids

34

,

35

to be rocked in an up-and-down direction in FIG.

2

.

Each of tension springs

47

,

48

has one end locked to a hook portion of the link member

38

or

39

and the other end locked to a hook portion of the frame of the device. When the solenoids

34

,

35

are in OFF conditions, the link members

36

,

37

are lifted upwardly (

FIG. 2

) by the tension forces of the tension springs.

[Operation of Flappers]

Next, the operation of the flappers during the sheet material sorting will be described.

FIGS. 1 and 2

show a solenoid OFF condition. In the condition that the solenoids

34

,

35

are OFF, the link members

36

,

37

are urged against an upper stopper

49

by the tension forces of the tension springs

47

,

48

and are stopped there. Accordingly, the flappers

81

to

86

are in their closed positions (shown by the solid lines in

FIG. 1

) where they do not block the common convey path

30

and form a part of the guide member defining the common convey path

30

. In this case, the flappers

81

to

86

are biased by biasing forces of compression springs

41

to

46

toward clockwise directions in

FIG. 2

(closing directions) around the rotation centers

81

a

to

86

a.

Now, for example, when the solenoid

34

(or solenoid

35

) is turned ON, the link member

36

(or link member

37

) is shifted downwardly (shown by the downwardly directed arrow in

FIG. 2

) in opposition to the tension force of the tension spring

47

(or tension spring

48

), with the result that the first, third and fifth flappers

81

,

83

,

85

(or second, fourth and sixth flappers

82

,

84

,

86

) are rocked in counter-clockwise directions in

FIG. 2

to reach the open positions (shown by the chain double-dashing lines in

FIG. 1

) for blocking the common convey path

30

. In this case, the first, third and fifth flappers

81

,

83

,

85

(or second, fourth and sixth flappers

82

,

84

,

86

) are biased by the biasing forces of compression springs

41

,

43

,

45

(or compression springs

42

,

44

,

46

) toward counter-clockwise directions in

FIG. 2

(opening directions) around the rotation centers

81

a,

83

a,

85

a

(or rotation centers

82

a,

84

a,

86

a

).

[Explanation of Upper and Lower Sensors]

The common convey path

30

further includes upper sensors (first detecting means)

91

,

92

for detecting the sheet material to control the open/close timing of the flappers, and lower sensors (second detecting means)

93

,

94

for detecting the sheet material jam. The lower sensors

93

,

94

also act to detect the sheet material to control the open/close timing of the flappers. In the illustrated embodiment, the open/close timing of the first to fourth flappers

81

,

82

,

83

,

84

is controlled on the basis of a sheet material detection signal from the upper sensors

91

,

92

, and the open/close timing of the fifth and sixth flappers

85

,

86

is controlled on the basis of a sheet material detection signal from the lower sensors

93

,

94

.

The upper sensors

91

,

92

are disposed at an upstream side of the uppermost first flapper

81

(for example, at an upstream side of the tip end of the flapper

81

by about 30 mm), and the lower sensors

93

,

94

are disposed at a downstream side of the upper sensors

91

,

92

with a predetermined distance (smallest size of the sheet material+α (larger than the smallest size of the sheet material by α)) therebetween. With this arrangement, the sheet material jam can surely be detected, and the open/close timing of the flappers for directing the sheet materials to the stacking trays can surely be controlled without any error.

[Example of Sorting Operation]

Next, for explaining a series of operations, an example that the sheet materials are sorted and conveyed to the fourth stacking tray

54

(for example) will be described.

The sheet material on which the image was formed by the image forming apparatus

1

is transferred to the sheet material stacking device

10

, where, after the front surface and the rear surface of the sheet material is reversed, the leading end (trailing end prior to the reversing of the front surface and the rear surface of the sheet material) of the sheet material is detected by the upper sensors

91

,

92

at the inlet of the common convey path

30

. Then, the sheet material is conveyed downwardly through the common convey path

30

at a predetermined speed by the pair of conveying rollers

31

. On the detection signal from the sensors

91

,

92

, at a timing when the leading end of the sheet material passes through the third flapper

83

, the solenoid

35

is turned ON.

When the solenoid

35

is turned ON, the link member

37

is pulled downwardly in

FIG. 2

with the result that the second, fourth and sixth flappers

82

,

84

,

86

are rocked in the counter-clockwise directions in FIG.

2

. The biasing force of the compression spring

42

for connecting the second flapper

82

to the link member

37

is selected to a value sufficient to be greater than the rocking resistance of the flapper

82

and smaller than rigidity of the sheet material being conveyed. Thus, during the rocking movement of the second flapper

82

to the open position where the common convey path

30

is blocked, when the tip end of the flapper abuts against the sheet material being conveyed through the common convey path

30

, due to the rigidity of the sheet material, the flapper

82

is stopped in opposition to the biasing force of the compression spring

42

at the position where the flapper abuts against the sheet material without blocking the common convey path

30

.

On the other hand, the fourth flapper

84

(and the sixth flapper

86

) are rocked to the open positions where the common convey path

30

is blocked. The sheet material is conveyed downwardly by the pair of the conveying rollers

31

of the common convey path

30

until it abuts against the fourth flapper

84

rocked to the open position. In this case, since a force obtained by abutting the leading end of the sheet material against the fourth flapper

84

is oriented to a direction tending to rotate the flapper

84

in the counter-clockwise direction in

FIG. 2

, the sheet material is positively guided toward the fourth pair of discharging rollers

74

, with the result that the sheet material is discharged onto the fourth stacking tray

54

by the pair of discharging rollers

74

.

In this case, although the sheet material is slidingly contacted with the tip end of the second flapper

82

, since the tip end (contacted with the sheet material) of the second flapper

82

has a round-configuration as shown, the sheet material is smoothly slid frictionally without being caught by the tip end of the flapper and is conveyed downwardly by the pair of conveying rollers

31

disposed at the downstream side of the flapper

82

.

Although not explained here, the operations of the third flapper

83

, fifth flapper

85

and sixth flapper

86

for guiding the sheet material to the discharge openings

63

,

65

,

66

are the same as the above-mentioned operation. Further, the biasing forces of the compression springs

41

,

43

,

44

,

45

,

46

are similarly set to the biasing force of the compression spring

42

. Similar to the flapper

82

, the tip ends (contacted with the sheet material) of the flappers

81

,

83

,

84

,

85

,

86

have round configurations.

With the arrangement as mentioned above, when the sheet material is discharged onto the lowermost (seventh in the illustrated embodiment) stacking tray

57

, all of the flappers are not operated (the solenoids

34

,

35

are in the OFF conditions), with the result that the sheet material is directed to the discharge opening

67

through the common convey path

30

, where the sheet material is discharged onto the stacking tray

57

by the pair of discharging rollers

77

.

By adopting the arrangement in which the alternate three flappers are operated by one solenoid as mentioned above, when the sheet material is guided toward the pair of discharging rollers by the third or fourth flapper

83

or

84

, the sheet material is slidingly contacted with the first or second flapper

81

or

82

, and, when the sheet material is guided toward the pair of discharging rollers by the fifth or sixth flapper

85

or

86

, the sheet material is slidingly contacted with the first and third flappers

81

,

83

or the second and fourth flappers

82

,

84

. In order to prevent the sheet material from being restrained due to the sliding contact between the sheet material and the flappers, the pairs of conveying rollers

31

to

33

disposed in the common convey path

30

are set to have conveying forces sufficiently greater than the sliding resistance.

Sheet pressing levers

95

,

96

are arranged in a widthwise direction of a sheet to correct curling of the sheet. As mentioned above, since the compression springs

41

to

46

are interposed between the flappers

81

to

86

and the link members

36

,

37

connected to the solenoids

34

,

35

in the transverse direction (substantially perpendicular to the common convey path

30

) to rock the flappers

81

to

86

by the compression springs

41

to

46

, even when the alternate three flappers are operated by one solenoid, the flappers other than the flapper effecting the sorting operation (flapper blocking the common convey path) do not restrain the sheet material. Accordingly, a sheet material stacking device which is cheaper and more compact, can effect stable sheet material conveyance and has high reliability can be provided.

Next, a stacking tray having an extension tray according to the present invention will be explained with reference to

FIGS. 4A

,

4

B,

4

C and

FIGS. 5A and 5B

.

FIG. 4A

is a plan view showing a stacking tray (sheet material stacking means)

51

, and an extension (elongation) tray (extension stacking means)

501

expansibly (retractably) mounted to the stacking tray

51

, and

FIG. 5A

is a plan view showing a condition that the extension tray

501

is extended.

The extension tray

501

is provided at its both lateral (upper and lower in

FIG. 4A

or

5

A) edges with guide ridges

502

. By slidingly fitting the guide ridges

502

into corresponding guide grooves

51

b

of the stacking tray

51

, the extension tray

501

can be expanded and contracted with respect to the stacking tray

51

.

A recess portion opened upwardly and extending from a substantially central portion of the stacking tray

51

toward a downstream side is formed in the stacking tray

51

. The extension tray

501

is mounted to the stacking tray

51

in such a manner that the extension tray is housed within the recess portion. As shown in

FIG. 4B

, a sheet material stacking surface of the extension tray

501

is flush with the stacking surface of the stacking tray

51

. The stacking tray

51

and the extension tray

501

have notches

51

a,

501

a

for facilitating the removal of the stacked sheet materials.

An upstream end (right end in

FIG. 4A

) of the extension tray

501

has a convex curvature and an upstream end of the recess portion of the stacking tray

51

has a corresponding concave curvature. The upstream end of the extension tray

501

has an inclined surface

505

which is curved along the convex curvature, as shown in FIG.

4

A.

The inclined surface

505

has a stepped portion

503

at its width-wise (transverse to the sheet material conveying direction) central portion thereof, which stepped portion is slightly protruded from the inclined surface

505

toward the upstream side. The stepped portion

503

serves to prevent the leading end of the sheet material being discharged onto the stacking tray

51

from being caught by the extension tray

501

. The stepped portion

503

is protruded from the inclined surface

505

by about 1 mm or 2 mm.

As shown in

FIG. 4C

, the stepped portion

503

is further extended downwardly to be fitted into an elongated slot

51

c

formed in the rear surface of the stacking tray

51

, and, as shown in

FIG. 5A

, there are provided a pair of projections

504

extending from the extension of the stepped portion

503

in the width-wise direction. The projections

504

are slidingly contacted with the rear surface of the stacking tray

51

on both sides of the elongated slot

51

c.

The stacking tray

51

is pinched between the guide ridges

502

and the projections

504

.

The projections

504

serve to prevent the sheet material from being pinched in a space between the stacking tray

51

and the stepped portion

503

of the extension tray

501

. Since the projections

504

are contacted with the rear surface of the stacking tray

51

, when the extension tray

501

is extended, camber of the extension tray

501

and formation of space therefor can be prevented.

FIG. 5A

is a plan view showing a condition that the extension tray

501

is extended when a large sized sheet material is discharged, and

FIG. 5B

is a sectional view taken along the line

5

B—

5

B in FIG.

5

A.

When the sheet material having a small size is discharged in the condition that the extension tray

501

is retracted into the stacking tray

51

as shown in

FIGS. 4A

to

4

C, or when the sheet material having a large size is discharged in the condition that the extension tray

501

is extended as shown in

FIGS. 5A and 5B

, the discharged sheet material is received by the stepped portion

503

of the extension tray

501

and is smoothly rested on the stacking tray

51

and the extension tray

501

while being guided by the inclined surface

505

.

As mentioned above, according to the present invention, since the extension stacking means can be extended and retracted with respect to the sheet material stacking means and the inclined surface is provided at the upstream end of the extension stacking means, the sheet material being discharged onto the sheet material stacking means can be prevented from being caught by the upstream end of the extension stacking means, thereby preventing the poor sheet material conveyance.

Further, since the stacking surface of the extension stacking means is flush with the stacking surface of the sheet material stacking means, a thin sheet material stacking means without catching the sheet material can be obtained, and installation space and the height of the device can be reduced.

Sheet material stacking device and image forming apparatus having same

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (1)