Device for removing a substance deposited on a sheet

This application is a division of application Ser. No. 09/154,497 filed on Sep. 17, 1998, pending, which is a divisional of application Ser. No. 08/869,970, filed Jun. 5, 1997, now U.S. Pat. No. 5,855,734, which is a divisional of application Ser. No. 08/542,905, filed Oct. 13, 1995, now U.S. Pat. No. 5,735,009.

BACKGROUND OF THE INVENTION

The present invention relates to a device for removing a substance deposited on the surface of a sheet and, more particularly, to a device for removing toner or similar image forming substance from the surface of a recording sheet.

A device having the above capability has recently been proposed in order to recycle recording sheets carrying images formed by an electrophotographic copier or similar image forming apparatus. Usually, an image formed on a sheet consists of relatively thick and large masses of toner forming major parts of the image, and fine solitary toner particles spaced from the masses. The conventional device has a problem that because many of the solitary toner particles exist around the edges of the image, a separating member included in the device cannot remove all the solitary particles from the sheet. Another problem is that the separating member cannot be smoothly separated from the sheet and is apt to be damaged.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a device capable of surely removing the entire substance deposited on a sheet.

It is another object of the present invention to provide a device for removing a substance deposited on a sheet, and capable of smoothly separating the sheet from a separating member while causing a minimum of damage to the separating member.

In accordance with the present invention, a device for removing a substance deposited on the surface of a sheet has a separating member for exerting, when brought into contact with the substance on the sheet, an adhering force on the substance, and for separating the substance from the sheet when separated from the sheet. A back-up member backs up the rear of the separating member moving with the sheet contacting it. A pressing member faces the back-up member, and presses the sheet and separating member. Projections are formed on the surface of the back-up member on which the rear of the separating member slides.

Also, in accordance with the present invention, a device for removing a substance deposited on the surface of a sheet has a separating member for exerting, when brought into contact with the substance on the sheet, an adhering force on the substance, and for separating the substance from the sheet when separated from the sheet. A back-up member backs up the rear of the separating member moving with the sheet contacting it. A pressing member faces the back-up member, and presses the sheet and separating member. A moving device causes at least a part of the sheet and at least a part of the separating member, once brought into contact with each other and then separated, to again contact each other, and then moves the sheet and separating member.

Further, in accordance with the present invention, a device for removing a substance deposited on the surface of a sheet has a separating member for exerting, when brought into contact with the substance on the sheet, an adhering force on the substances and for separating the substance from the sheet when separated from the sheet. The separating member is movable along an endless path with the sheet contacting it. A back-up member backs up the rear of the separating member. A separator roller separates the sheet from the separating member. The back-up member and separator roller are located inside of the endless path and downstream, in the intended direction of sheet transport, of a nip where the sheet and separator roller contact each other. Grooves are formed in the separator roller at predetermined intervals in the axial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:

FIG. 1A

is a perspective view showing a specific configuration of a heat block representative of an embodiment of the present invention;

FIG. 1B

is an enlarged perspective view of a nip particular to the heat block;

FIG. 2

is a perspective view showing another specific configuration of the heat block.

FIG. 3

is a sketch demonstrating how solitary toner partcles contact a belt in any of the configurations of

FIGS. 1 and 1B

and

2

;

FIG. 4

is a graph representative of a specific drive pattern for driving a drive roller included in a toner separator unit;

FIG. 5A

is a section of a toner separating unit in accordance with the present invention;

FIG. 5B

is a section of a separator roller included in the unit of

FIG. 5A

;

FIG. 5C

shows a guide member contacting the separator roller of

FIG. 5A

;

FIG. 6

shows a relation between sheet widths and grooves formed in the separator roller of

FIG. 5B

;

FIG. 7

is a section of another toner separating unit with which the present invention is practicable;

FIG. 8A

is a section showing still another toner separating unit with which the present invention is practicable;

FIG. 8B

is a perspective view of a heat block included in the unit of

FIG. 5A

;

FIGS. 9 and 10

are sections each showing a particular conventional device for removing toner from a sheet;

FIG. 11

is a sketch showing how solitary toners and a belt contact at a nip included in any of the conventional devices; and

FIG. 12

is a section of a conventional toner separator unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

To better understand the present invention, a brief reference will be made to conventional devices for removing toner or similar image forming substance deposited on a recording sheet, shown in

FIGS. 9 and 10

.

The device shown in

FIG. 9

has a sheet feeding unit

20

accommodating a stack of sheets or recordings

10

each carrying a toner image thereon. The sheets

10

are fed from the unit

20

one by one. A liquid applying unit

30

applies a parting liquid to the sheet

10

fed from the unit

20

. A toner separating unit, or separating means,

40

separates the toner from the sheet

10

come out of the liquid applying unit

30

. A drying unit

60

dries the sheet

10

from which the toner has been separated by the separating unit

40

. The sheet

10

coming out of the drying unit

60

is driven out to a tray unit

70

.

In operation, when the sheet

10

from the feeding unit

20

is introduced into the liquid applying unit

30

, the unit

30

applies the parting liquid evenly over the entire surface of the sheet

10

on which a toner image is carried. Let this surface be referred to an image surface hereinafter. Then, the sheet

10

is conveyed into the toner separating unit

40

. The unit

40

softens the toner deposited on the sheet

10

with a heat roller

45

and a support member

46

. The support member or back-up member

46

supports a belt or toner separating member

44

. As a result, the toner softened on the sheet

10

adheres to the surface of the belt

44

. When the sheet

10

is separated from the belt

44

by a separator roller

43

, the toner is transferred from the sheet

10

to the belt

44

.

The device shown in

FIG. 10

has a heat block

46

a

in place of the back-up member

46

. The function of the separator roller

43

,

FIG. 9

, is assigned to one corner

46

′

a

of the beat block

46

a

positioned at the downstream side in the intended direction of sheet feed. As to the rest of the construction, the device of

FIG. 10

is similar to the device of FIG.

9

. The sheet feeding unit

20

and tray unit

70

are not shown in FIG.

10

.

Generally, an image formed on a sheet by a copier using dry toner is constituted by toner particles having a particle size of several microns to 10 and some microns. Such toner is transferred to and fixed on the sheet in substantially a single layer. The image is made up of relatively thick and large masses of toner particles forming the major parts of the image, and small solitary toner particles spaced apart from the masses, as stated earlier. Many of the solitary particles exist around the edges of the image. With the device shown in

FIG. 9

or

10

, it is likely that the solitary particles on the sheet

10

fail to closely contact the belt

44

and, as a result, remain on the sheet

10

. Specifically, as shown in

FIG. 11

, assume that solitary particles P adjoin relatively thick masses of toner particles Q. Then, when the sheet

10

is passed through the separating unit

40

, the masses Q support the sheet

10

and prevent the particles P from contacting the belt

44

.

As shown in

FIG. 10

, the portion for separating the sheet

10

from the belt

44

is implemented by the corner

46

′

a

of the heat block

46

a

downstream of a nip between the block

46

a

and the heat roller

45

. The corner

46

′

a

sharply changes the direction in which the belt

44

runs, thereby separating the sheet

10

from the belt

44

on the basis of curvature. However, if the adhesion acting between the belt

44

and the sheet

10

is increased in order to enhance the efficient separation of the masses Q,

FIG. 11

, it is likely that the belt

44

and sheet

10

fail to separate from each other. Moreover, when the moving direction of the belt

44

is changed more sharply by the corner

46

′

a

, a greater frictional force acts on the belt

44

. As a result, a load to act on drive means for driving the belt

44

increases and thereby scales up the driving means. In addition, an excessive force is apt to act on the belt

44

at the corner

46

′

a

and damage it.

The present invention capable of obviating the above problems particular to the conventional devices will be described hereinafter. The present invention is implemented as a device for removing toner deposited on a sheet by an electrophotographic copier by way of example. For the following description, a reference will be made to

FIG. 9

except for the characteristic features of the present invention.

Basically, the toner removing device is made up of the various units shown in

FIG. 9

, i.e., sheet feeding unit

20

, liquid applying unit

30

, separating unit

40

, drying unit

60

, and tray unit

70

. The sheets

10

are stacked on a tray

21

included in the sheet feeding unit

20

face down, i.e., their image surfaces facing downward. A pick-up roller

22

feeds the lowermost sheet

10

out of the unit

20

. At this instant, a separator roller pair

23

separates the lowermost sheet

10

from the overlying sheets

10

, so that only the lowermost sheet

10

is fed out by a feed roller pair

24

. The construction and operation of the unit

20

is substantially identical with those of a sheet feed unit customarily included in an electrophotographic copier and will not be described specifically.

The liquid applying unit

30

applies to the sheet

10

a parting liquid

31

which may be water or an aqueous solution containing a surfactant. The surfactant promotes the permeation of the liquid into the sheet

10

. The unit

30

has a vessel

32

filled with the liquid

31

, an applicator roller

33

partly immersed in the liquid

31

and rotatable for applying the liquid

31

to the image surface of the sheet

10

, and a regulator roller, or sheet regulating member,

34

facing the applicator roller

33

with the intermediary of a sheet transport path. The applicator roller

33

may be formed to a hydrophilic porous material, sponge or similar material capable of retaining a liquid therein, or rubber or similar elastic material, or metal or similar rigid material. A first sheet guide mechanism

35

guides the sheet

10

fed from the unit

20

to the nip between the applicator roller

33

and the regulator roller

34

. The nip will be referred to as a liquid applying position hereinafter. A second sheet guide mechanism

36

guides the sheet

10

coming out of the liquid applying position to the toner separating unit

40

.

The toner separating unit

40

bas a plurality of support rollers

41

,

42

and

43

over which the belt

44

is passed, the heat roller

45

and back-up member

46

respectively accommodating lamps or heaters

45

′ and

46

′, and a belt cleaning device

49

for removing the toner from the surface of the belt

44

. At least the surface of the belt

44

is made of a material causing the softened toner to adhere thereto more intensely than to the surface of the sheet

10

. For example, the entire belt

44

is formed of aluminum-, copper- or nickel-based metal, or polyethylene terephthalate (PET) in which titanium oxide is dispersed or similar material having a high molecular weight.

The part of the belt

44

coming out of the nip between the heat roller

45

and the back-up roller

46

is passed over the support roller, or separator roller as referred to hereinafter,

43

. The separator roller

43

sharply changes the direction in which the belt

44

runs, thereby separating the sheet

10

from the belt

44

on the basis of curvature. A guide roller

48

presses the portion of the belt

44

between the separator roller

43

and the support roller

41

, which faces the belt cleaning unit

49

, inward so as to increase the change in the moving direction of the belt

44

. The belt

44

is driven by the support roller or drive roller

42

. The heat roller

45

and back-up member

46

soften the toner deposited on the paper

10

while causing the image surface of the sheet

10

to closely contact the surface of the belt

44

.

Because the masses of toner support the surface of the sheet

10

, it is likely that the solitary toner particles fall to closely contact the belt

44

and, as a result, remain on the sheet

10

, as stated earlier. To enhance the close contact of the solitary particles with the belt

44

, the present invention uses the heat block

46

a

,

FIG. 10

, having a plurality of projections at the nip or uses the drive roller

42

as moving means. In this condition, the sheet

10

is passed through the toner separating unit

40

a plurality of times, as will be described specifically later.

The belt cleaning device

49

has a rotatable brusb roller

50

for scraping off the toner from the belt

44

. A pad

51

is held in contact with the belt

44

at a position downstream of the brush roller SO in the direction of movement of the belt

44

. The pad

51

removes the toner from the belt

44

by scrubbing the belt

44

. The toner removed from the belt

44

is collected in a casing

52

.

Further, in the toner separating unit

40

, a conveyor roller pair

53

conveys the sheet

10

coming out of the liquid applying unit

30

into the nip between the heat roller

45

and the back-up member

46

. An upper and a lower guide member

54

cooperate to guide the sheet

10

separated from the belt

44

by the separator roller

43

toward the drying unit

60

. The separator roller

43

will also be described specifically later.

The drying unit

60

dries the sheet

10

such that the sheet

10

retains the liquid

31

in an amount which is, for example, less than 10% of its own weight. The unit

60

has a heat drum

61

made of, e.g., aluminum and having a lamp

61

′ therein. A belt

63

is passed over a plurality of support rollers

62

and movable while wrapping around the heat drum

61

over a preselected angle. One of the support rollers

62

plays the role of a tension roller. The belt

63

is implemented by a heat-resistant and air-permeable material, e.g., canvas, cotton, or Tetron. An upper and a lower guide member

64

guide the sheet

10

coming out of the region where the drum

61

and belt

63

contact each other. An outlet roller pair

65

drives the sheet

10

from the guide members

64

onto a tray included in the tray unit

70

.

In operation, when the sheet

10

from the sheet feed unit

20

is introduced into the liquid applying unit

30

, the unit

30

applies the parting liquid

31

evenly over the entire image surface of the sheet

10

on which a toner image is carried. Then, the sheet

10

is conveyed into the toner separating unit

40

. The unit

40

softens the toner deposited on the sheet

10

with the heat roller

45

and back-up member

46

. As a result, the toner softened on the sheet

10

adheres to the surface of the belt

44

. When the sheet

10

is separated from the belt

44

by the separator roller

43

, the toner is transferred from the sheet

10

to the belt

44

. Subsequently, the sheet

10

is dried by the drying unit

6

and then driven out to the tray unit

70

.

As stated above, the liquid applied to the sheet

10

penetrates into the interface between the paper

10

and the toner and thereby causes the toner to be separated from the sheet

10

. This successfully removes the toner from the sheet

10

without damaging the fibers of the sheet

10

.

Referring

FIGS. 1A

,

1

B,

2

,

3

and

4

, specific configurations of the toner separating unit

40

representative of embodiments of the present invention will be described which prevent the toner, particularly solitary toner particles, from remaining on the sheet

10

.

FIGS. 1A and 1B

show a specific configuration of the heat block

46

a

representative of the toner separator unit

40

. This unit

40

is identical with the unit

40

shown in

FIG. 9

except for the heat block

46

a

. As shown, the block

46

a

has a plurality of projections

47

in the nip or pressing portion L thereof. The downstream corner

46

′

a

of the block

46

a

serves to separate the sheet

10

from the belt

44

. Specifically, as shown in

FIG. 1B

in an enlarged view, a plurality of arrays of projections

47

are formed on the surface of the block

46

a

that face the image surface of the sheet

10

. Let this surface of he block

46

a

be referred to as a front hereinafter. The arrays of projections

47

are spaced from catch other in the direction of sheet transport, and catch extends perpendicularly to the direction of sheet transport. Further, the arrays are arranged in a zigzag configuration such that the projections

47

of nearby arrays are not aligned in the direction of sheet transport. The projections

47

are 10 microns to several hundreds of microns high each (H). In this configuration, while the sheet

10

is passed through the nip L, the projections

47

raise the portions of the front of the belt

44

corresponding to the portions of the rear of the belt

44

contacting the projections

47

toward the image surface of the sheet

10

a plurality of times.

More specifically, an shown in

FIG. 3

, the sheet

10

is passed through the nip L, which is several millimeters wide, together with the belt

44

. At this instant, the projections

47

raise the above-mentioned portions of the belt

44

toward the image surface of be sheet

10

a plurality of times. Hence, despite that the solitary toner particles P exist in the vicinity of the relatively thick and large masses of toner Q, they are successfully brought into contact with the portions

44

′ of the front of the belt

44

raised by the projections

47

. Subsequently, the toner particles are separated from the sheet

10

when the sheet

10

is separated from the belt

44

around the corner

46

′

a

of the block

46

a

. As a result, the masses Q, particularly solitary particles P, are prevented from remaining on the sheet

10

. It is noteworthy that the projections

47

have no influence on the pressure distribution at the nip L. The number of projections

47

is open to choice.

FIG. 2

shows another specific configuration of the heat block

46

a

. The toner separating unit

40

with the block

46

a

is identical with the unit

40

of

FIG. 9

except for the block

46

a.

As shown, the projections

47

are formed on a single movable member

47

′. The member

47

is positioned at the nip L defined on the front of the block

46

a

and movable in a reciprocating motion perpendicularly to the direction of sheet transport. A plurality of arrays of projections

47

are formed on the front of the block

46

a

that faces the image surface of the sheet

10

. The arrays of projections

47

are spaced from each other in the direction of sheet transport, and each extends perpendicularly to the direction of sheet transport. Further, the arrays are arranged in a zigzag configuration such that the projections

47

of nearby arrays are not aligned in the direction of sheet transport. The projections

47

are

10

microns to several hundreds of microns high each.

When the movable member

47

′ is moved back and forth in the direction perpendicular to the direction of sheet transport, the projections

47

are moved in the same direction. In this condition, while the sheet

10

is passed through the nip L, the front of the belt

44

is raised by the projections

47

widthwise toward the image surface of the sheet

10

. This causes the belt

44

to contact the sheet

10

over a broader area than when the projections

47

are not movable. As a result, the solitary particles P contact the belt

44

more frequently than in the configuration of

FIGS. 1A and 1B

. Hence, the masses Q, particularly solitary particles P, are prevented from remaining on the sheet

10

.

Again, the projections

47

have no influence on the pressure distribution at the nip L. While the speed at which the member

47

′ moves is open to choice, it should preferably be selected in consideration of the amount of toner to deposit on the sheet

10

and how many times the belt

44

is to be raised toward the sheet

10

.

Hereinafter will be described another alternative embodiment of the present invention including the toner separator unit

40

which has the drive roller

42

and back-up member or roller

46

. The unit

40

is identical with the unit

40

shown in

FIG. 9

except that the drive roller

42

is reversible. The drive roller

42

is reversibly driven by, e.g., a reversible motor.

FIG. 4

shows a specific velocity pattern for driving the drive roller

42

. With the velocity pattern of

FIG. 4

, the drive roller

42

causes a single sheet

10

to move back and forth via the nip a plurality of times, as follows. First, the roller

42

is driven forward to move the sheet

10

past the nip at a velocity of V until the sheet

10

has been separated from the belt

44

by the separator roller

43

except for the trailing edge portion thereof. Then, the roller

42

is reversed to return the sheet

10

toward the nip at a velocity of V/2. After the sheet to has moved away from the nip, the roller

42

is again rotated forward to drive the sheet

10

toward the separator roller

43

at the velocity of V. In the illustrative embodiment, the roller

42

causes the sheet

10

to move via the nip four consecutive times.

Assume that when the sheet

10

partly separated from the belt

44

by the separator roller

43

is returned to and passed through the nip in the reverse direction, it again contacts the belt

44

in exactly the same position as during the forward movement. Then, it is likely that the solitary particles P failed to contact the belt

44

last time due to the masses Q again fail to contact it. In the illustrative embodiment, when the sheetheld in contact with the belt

44

is partly separated by the separator roller

43

, it is in a contracted condition because water has been evaporated by the heat applied thereto at the nip. As a result, when the sheet

10

is returned to the nip by the roller

43

, the positionally relation between the sheet

10

and the belt

44

is different from the previous relation. This prevents the sheet

10

from contacting the belt

44

in the same position as before. It follows that the solitary particles P failed to contact the belt

44

last time possibly contact it at a different position when the sheet

10

is again passed through the nip.

When the sheet

10

is separated from the belt

44

around the separator roller

43

, the solitary particles P adhered to the belt

44

are separated from the sheet

10

. In this manner, the particles P contact the belt

44

more frequency. This prevents the masses Q, particularly solitary particles P, from remaining on the sheet

10

.

Because the sheet

10

contains water even after it has been passed through the nip, the masses Q and solitary particles P are prevented from being again fixed on the sheet

10

despite the return of the sheet

10

. It is to be notice that the velocity pattern shown in

FIG. 4

is only illustrative, and that the number of times of separation by the separator roller

43

and the number of times of reciprocating movement are open to choice.

If desired, the beat block

46

a

shown in

FIGS. 1A and 1B

or

FIG. 2

may be combined with the reversible drive roller

42

. In this combination, the solitary particles P contact the surface portions of the belt

44

raised by the projections

47

toward the image surface of the sheet

10

. In addition, the particles P failed to contact the belt

44

last time are allowed to contact it when the sheet

10

is moved back and forth via the nip a plurality of times. This successfully increases the number of times that the partcles P contact the belt

44

. While the sheet

10

has been described as being partly separated from the belt

44

before its return toward the nip, the drive roller

42

may be so controlled as to fully separate the sheet

10

from the belt

44

, in which case returning means will be used to return the separated sheet

10

and belt

44

toward the nip.

In the foregoing embodiments, the sheet

10

moved away from the nip is separated from the belt

44

by curvature, i.e., the sharp change in the direction in which the belt

44

runs. However, when the adhesion acting between the sheet

10

and the belt

44

is intense, it is likely that they cannot be surely separated from each other. The separator roller

43

shown in

FIG. 9

is capable of reducing friction between it and the belt

44

and, therefore, the load to act on the belt

44

, compared to the corner

46

′

a

of the heat block

46

a

shown in FIG.

12

. However, because the curvature of the roller

43

is greater than that of the corner

46

a

′, the simple roller scheme lowers the separating ability, compared to the heat block scheme.

FIG. 5A

shows a specific configuration of the toner separating unit

40

applicable to the device shown in

FIG. 9

or

10

, and capable of surely obviating the defective separation mentioned above.

FIG. 5B

is a section along the axis of the separator roller

43

.

FIG. 5C

shows a sheet guide

54

contacting the separator roller

43

and playing the role of a separator at the same time. As shown in

FIG. 5B

, a plurality of circumferential grooves

80

are formed in the separator roller

43

at predetermined intervals in the axial direction. Further, as shown in

FIG. 5C

, the sheet guide

54

is held in contact with the bottom of each groove

80

so as to physically separate the sheet

10

from the belt

44

. As shown in

FIG. 6

, the grooves

80

are positioned in matching relation to various sheet sizes. i.e., such that the center of any one of the grooves

80

is spaced a predetermined distance L inward from one edge of the sheet of particular size in the widthwise direction. In practice, therefore, a plurality of sheet guides

54

are respectively received in the grooves

80

of the roller

43

.

In the above configuration, at the position where the sheet is released from the force of the heat roller

45

and to be separated from the belt

44

, it wraps around the grooves

80

of the roller

43

. As a result, the belt

44

held under a preselected degree of tension is instantaneously deformed complementarily to the configuration of the grooves

80

and waves in the axial direction of the roller

43

. On the other hand, the sheet

10

remains in contact with the belt

44

with the intermediary of the toner and maintains some elasticity although it is wet. This, coupled with the fact that the sheet

10

is free from tension, prevents the sheet

10

from following the instantaneous waving of the belt

44

. Consequently, the sheet and the portions of the belt

44

corresponding to the grooves

80

are spaced apart from each other, or at least the adhesion acting therebetween is reduced. Hence, the separation of the sheet

10

to follow and relying on curvature is effected more desirably than when the belt

44

is not deformed along the grooves

80

.

Moreover, the sheet guides

54

separate the sheet

10

from the belt

44

after the adhesion acting therebetween has been reduced. Hence, even if the guides

54

are not strongly pressed against the belt

44

, the sheet

10

is surely separated from the belt

44

. In addition, the load on the belt

44

and attributable to the guides

54

is reduced.

FIG. 6

shows a case wherein sheets

10

of different sizes are conveyed along a single center line in the widthwise direction. When sheets of different sizes are conveyed while being commonly positioned at a single edge, the distance between the nearby grooves

80

will be determined on the basis of the single edge.

FIG. 7

shows an upper and a lower separator roller

43

a

and

43

b

, respectively, each being formed with the grooves

80

. The rollers

43

and

43

b

are applied to a toner separating unit

40

of the type capable of removing toner from both sides of a sheet

10

at the same time. As shown, a sheet

10

carrying a toner image on both sides thereof is introduced into the unit

40

by a roller pair

53

. Arranged in the unit

40

are an upper belt

44

a

and a lower belt

44

b

. The upper belt

44

a

is supported by a tension roller

83

, a plurality of support rollers

82

, and the upper separator roller

43

a

. Likewise, the lower belt

44

b

is supported by a tension roller

83

, a plurality of support rollers

82

, and the lower separator roller

43

b

. A plurality of heat rollers

45

and

46

define the nips of the upper and lower belts

44

a

and

44

b

. The sheet

10

is sequentially conveyed by the belts

44

a

and

44

b