Tube pump and ink jet recording apparatus using the tube pump

BACKGROUND OF THE INVENTION

This invention relates to a tube pump using deformation of a tube for generating pressure and an ink jet recording apparatus comprising recovery device of an ink ejection capability for discharging ink from a recording head using negative pressure generated by the tube pump.

An ink jet recording apparatus produces comparatively small noise at the printing time and moreover can form small dots at a high density and thus nowadays is widely used for print centering on color print.

Such an ink jet recording apparatus comprises an ink jet recording head for receiving ink supplied from an ink cartridge and paper feed device for relatively moving record paper to the recording head.

While the recording head is moved in response to a print signal, ink droplets are ejected onto record paper for forming dots, thereby recording. In this case, a recording head capable of ejecting black ink, yellow ink, cyan ink, and magenta ink, for example, is mounted on a carriage and the ink ejection percentage is changed, thereby making full color print possible.

Since such an ink jet recording apparatus ejects ink onto record paper as ink droplets through nozzle openings for printing, it involves the following problem: clogging occurs in the nozzle openings due to a rise in ink viscosity caused by evaporation of an ink solvent from the nozzle openings, ink solidification on the nozzle formation face, or deposition of dust and further air bubbles are mixed into the recording head, causing a print failure to occur.

Thus, in addition to the recording head and the paper feed device, the ink jet recording apparatus comprises capping device for sealing the nozzle formation face of the recording head in a non-print mode, a suction pump for sucking and discharging ink into the capping device, and wiping device for cleaning the nozzle formation face of the recording head after ink is sucked and discharged by the suction pump.

To prevent clogging from occurring in the nozzle openings and air bubbles from being mixed into the recording head, ink is forcibly sucked and discharged from the recording head into the capping device by the suction pump (ink ejection capability recovery processing) and then the nozzle formation face of the recording head is wiped by the wiping device.

The forcible discharge processing of ink performed to remove clogging of the recording head or if air bubbles remain in the recording head is called cleaning operation. The cleaning operation is performed when print is restarted after the recording apparatus is in a nonoperating mode for a long time or when the user recognizes a print quality failure of faint print, etc., and presses a cleaning switch.

To perform the cleaning operation, the recording head is sealed with the capping device and a negative pressure is made to act on the inside of the capping device.

Used as a device for feeding a negative pressure into the capping device is a tube pump which has a comparatively simple structure, can be easily miniaturized, and moreover does not cause pollution in the mechanical portion for sucking and discharging ink.

The tube pump has a configuration, for example, as shown in

FIGS. 7 and 8

.

FIG. 7

shows a pump operation state as the pump is driven in a forward direction and

FIG. 8

shows a release operation state as the pump is driven in a reverse direction.

The tube pump shown in

FIGS. 7 and 8

comprises a pump frame

44

having a tube support face

52

for guiding the outer shape of a flexible tube

51

to be a circular-arc manner, a pump wheel

42

rotated by a paper feed motor, for example, and rollers

43

a

and

43

b

having roller shafts

43

A and

43

B moving along roller support grooves

42

a

and

42

b

opened to an end face of the pump wheel

42

.

The pump frame

44

is formed with L-shaped retention grooves

44

a

and

44

b

opposed to the tube support face

52

and guide members

53

a

and

53

b

made of elastic material projecting in the center direction of the pump wheel

42

are retained in the retention grooves

44

a

and

44

b.

In such a tube pump, if the pump wheel

42

is rotated in the normal direction (arrow A direction) as shown in

FIG. 7

, the rollers

43

a

and

43

b

move in the outer peripheral direction of the roller support grooves

42

a

and

42

b

and are rotated and rolled while pressing the flexible tube

51

in the arrow A direction. Accordingly, a pressure is generated in the flexible tube

51

for feeding a negative pressure into the capping device. Ink is forcibly discharged from the recording head by the negative pressure and further the ink discharged into the capping device is sucked and is sent to a waste ink tank.

If the pump wheel

42

is rotated in the reverse direction (arrow B direction) as shown in

FIG. 8

, the rollers

43

a

and

43

b

move in the inner peripheral direction of the roller support grooves

42

a

and

42

b

and are rotated and rolled in the arrow B direction while keeping the flexible tube

51

in the release operation state in which the rollers

43

a

and

43

b

come in contact with the flexible tube

51

only a little. Accordingly, failure occurrence of the roller

43

a

,

43

b

sticking to the flexible tube

51

or the like is prevented.

In this case, the guide members

53

a

and

53

b

act so as to guide the rollers

43

a

and

43

b

in the wheel rotation backward direction of the roller support grooves

42

a

and

42

b

as the pump wheel

42

is rotated.

However, in this kind of tube pump, when the pump operation state is switched to the release operation state, the rollers

43

a

and

43

b

rotate and roll with the pump wheel

42

while pressing the flexible tube

51

, and thus the following problem is involved. That is, just after the pump operation state is switched to the release operation state, the rollers

43

a

and

43

b

receive such a force displacing in the wheel rotation direction with the rollers

43

a

and

43

b

pressed into contact with the flexible tube

51

from the groove walls of the roller support grooves

42

a

and

42

b

and thus fluids of ink, air, etc. which are sucked into the flexible tube

51

flow back and the reliability on the pump quality is degraded.

On the other hand, to use the tube pump with the ink jet recording apparatus, ink bubbles are produced in the capping device because of flowback of ink, etc. which is sucked from the recording head and some of the ink bubbles may be exposed to the outside of the capping device.

If the ink bubbles are thus exposed to the outside of the capping device, when the recording head is next sealed with the capping device, as they come in contact with each other the ink bubbles are broken and this action may cause instantaneous air pressure change to occur in the nozzle openings of the recording head, destroying meniscuses of ink formed in the nozzle openings.

Consequently, the normal ejection operation of ink droplets through the nozzle openings cannot be accomplished, causing a print fault called missing dots to occur, leading to degradation of the reliability on cleaning; this is a problem.

It is therefore an object of the invention to provide a tube pump for making it possible to enhance reliability on pump quality, simplify the whole structure, and reduce costs and an ink jet recording apparatus using the tube pump to make it possible to enhance reliability on cleaning.

To this end, according to the invention, there is provided a tube pump comprising:

a pump frame having a tube support face for guiding a curve of a flexible tube in a circular-arc manner;

a pump wheel rotatably disposed in the pump frame and having a roller support groove; and

a roller having a roller shaft, disposed rotatably and rollably on the pump wheel and relatively displaceable between a pump operation position and a release operation position in the roller support groove, the roller being configured to deform the flexible tube by a press contact so as to generate a pressure in the tube pump;

the roller shaft being guided by a groove wall in contact therewith;

wherein the groove wall of the roller support groove is provided with a cam face configured such that

the roller is relatively displaced from the release operation position to the pump operation position in a state that the roller rotates and rolls, when the pump wheel rotates from a release operation state in a pump operation direction; and

the roller is relatively displaced from the pump operation position to the release operation position in a state that the roller does not rotate and roll, when the pump wheel rotates from a pump operation state in a release operation direction.

Since the tube pump is thus configured, when the release operation state is switched to the pump operation state, the roller rotates and rolls and receives such a force displacing from the release operation position to the pump operation position from the groove wall of the roller support groove. On the other hand, when the pump operation state is switched to the release operation state, the roller remains immobile and receives such a force displacing from the pump operation position to the release operation position from the groove wall of the roller support groove.

Therefore, just after the pump operation state is switched to the release operation state, the roller is prevented from rotating and rolling in the wheel rotation direction while pressing the flexible tube, so that fluids of ink, air, etc., sucked in the flexible tube do not flow back and the reliability on the pump quality can be enhanced.

Here, it is desirable that a cam curve of the cam face should be a curve with an arbitrary point on a line represented by polar coordinates (r, θ) wherein the rotation center of the pump wheel is the origin, radius r is a function of angle θ found from r=C

1

×exp (α·θ), and end angle θ

β

is a constant found from θ

β

=(1/α)×log (C

2

/C

1

), that polar coordinates (r, θ) of both end points on the curve should be set to predetermined polar coordinates (C

1

, 0) and (C

2

, θ

β

), and that pressure angle α of the cam face with respect to the roller shaft should be set to a predetermined angle in the range of π/30<α<π/20.

Since the tube pump is thus configured, if the pressure angle α is α=7π/180 (7°) or α=8π/180 (8°), just after the pump operation state is switched to the release operation state, the roller is prevented from rotating and rolling in the wheel rotation direction while pressing the flexible tube, so that the reliability on the pump quality can be enhanced.

If α=π/30 (6°), after the pump operation state is switched to the release operation state, the roller does not move toward the release operation position at an intermediate point of the roller support groove and moves interlockingly with the pump wheel while pressing the flexible tube. If α=π/20 (9°), just after the release operation state is switch to the pump operation state, the roller does not move toward the pump operation position and moves interlockingly with the pump wheel.

It is desirable that a roller guide having a guide face for guiding the roller shaft is placed on the axis of the pump wheel.

Since the tube pump is thus configured, when the roller shaft moves within the roller support groove, it is guided by the roller guide.

The tube support face may be provided such that the contact area between the flexible tube and the roller is formed all around the pump wheel.

Since the tube pump is thus configured, the contact area becomes long in the circumferential direction and thus a higher negative pressure can be provided as compared with the tube support face such that the contact area between the flexible tube and the roller is provided on half of the circumference of the pump wheel.

Further, the roller support groove is a single roller support groove at a position eccentric from the rotation center of the pump wheel.

Since the tube pump is thus configured, a single roller can be placed for the pump wheel.

The configuration wherein the roller support groove is a pair of roller support grooves positioned at parts symmetrical with respect to a point about the rotation center of the pump wheel can also be adopted.

Since the tube pump is thus configured, a pair of rollers can be placed for the pump wheel.

On the other hand, according to the invention, there is provided an ink jet recording apparatus comprising an ink jet recording head for ejecting ink droplets in response to print data; and capping device for sealing the nozzle formation face of the recording head and sucking and discharging ink from the recording head upon reception of a negative pressure from a pump unit, characterized by the above-described tube pump as the pump unit.

Since the ink jet recording apparatus is thus configured, fluids of ink, air, etc., sucked from the recording head can be prevented from flowing back into the capping device.

Therefore, ink bubbles produced as in the related art are not produced, so that destroying of meniscuses as ink bubbles are broken can be prevented.

Thus, the normal ejection operation of ink droplets through the nozzle openings can be accomplished, so that a print fault called missing dots does not occur and the reliability on cleaning can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view to show an outline of the basic configuration of an ink jet recording apparatus incorporating the invention;

FIG. 2

is a sectional view to show an example of drive power transmission device placed in the ink jet recording apparatus shown in

FIG. 1

;

FIG. 3

is a perspective view to show the main part of a tube pump according to a first embodiment of the invention;

FIG. 4

is a plan view to describe a groove wall of a roller support groove of a pump wheel in the tube pump according to the first embodiment of the invention;

FIG. 5

is a side view to show a roller between the pump wheel and a roller guide in the tube pump according to the first embodiment of the invention;

FIG. 6

is a perspective view to show the main part of a tube pump according to a second embodiment of the invention;

FIG. 7

is a perspective view to show a state in which a tube pump in a related art is driven in a forward direction for executing pump operation; and

FIG. 8

is a perspective view to show a release operation state as the tube pump in the related art is driven in a reverse direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An ink jet recording apparatus using a tube pump according to the invention will be discussed based on an embodiment shown in the accompanying drawings.

FIG. 1

is a perspective view to show an outline of the general configuration of the ink jet recording apparatus incorporating the invention.

In

FIG. 1

, a carriage indicated by numeral

1

can be reciprocated in the axial direction of a platen

5

as guided by a guide member

4

via a timing belt

3

driven by a carriage motor

2

.

The guide member

4

is supported on two left and right frames

31

and

32

opposed to each other. Both the frames

31

and

32

are joined by a rear plate

33

and a bottom plate

34

.

An ink jet recording head

12

is mounted on the lower face portion of the carriage

1

so that it is opposed to record paper

6

. A black ink cartridge

7

and a color ink cartridge

8

for supplying ink to the recording head

12

are detachably held on the upper face portion-of the carriage

1

.

A capping device

9

having a cap member

9

a

is placed in a non-print area (home position) in a move area of the carriage

1

. When the recording head

12

moves just above the capping device

9

, the capping device

9

can move up so as to seal the nozzle formation face of the recording head

12

. A tube pump

10

as a pump unit to give a negative pressure to the internal space of the cap member

9

a

is placed below the capping device

9

.

The capping device

9

has a function as a lid for preventing nozzle openings of the recording head

12

from being dried during the nonoperating period of the ink jet recording apparatus. It also has a function as an ink receiver during the flushing operation of applying a drive signal not involved in print to the recording head

12

for idly ejecting ink droplets and a function as cleaning device for causing a negative pressure from the tube pump

10

to act on the recording head

12

for sucking ink.

A wiping device

11

comprising an elastic plate of rubber, etc., is placed in the proximity of the print area side in the capping device

9

so that it can advance and retreat in a horizontal direction. When the carriage

1

reciprocates on the capping device

9

side, the wiping device

11

can advance onto the move path of the recording head

12

.

Next, a drive power transmission device to a paper feed and ejection mechanism and the suction pump (tube pump) placed in the ink jet recording apparatus will be discussed with reference to FIG.

2

.

FIG. 2

is a sectional view to show an example of the drive power transmission device to the paper feed and ejection mechanism and the suction pump placed in the ink jet recording apparatus incorporating the invention.

As shown in

FIG. 2

, numeral

21

denotes a paper feed roller and a gear

22

is placed at one end of the paper feed roller

21

. It is driven via an idler

25

from a pinion placed on the shaft of a paper feed motor

23

. A gear

27

is placed at one end of a paper feed roller drive shaft

26

and meshes with the gear

22

via a move gear

28

forming a part of a clutch mechanism for transmitting power to a cut sheet feeder (not shown) for feeding (loading) record paper.

The move gear

28

is held normally at a position distant from both the gears

22

and

27

by a spring (not shown). The move gear

28

is pressed by the carriage

1

moving to the end opposed to the home position and moves in an axial direction and is placed between both the gears

22

and

27

for allowing both the gears

22

and

27

to mesh with each other.

On the other hand, power from the paper feed motor

23

is transmitted to the pinion

24

, the idler

29

, and a paper ejection roller gear

30

on a paper ejection roller

31

and further power from the paper ejection roller gear

30

is transmitted to a gear

32

on the paper ejection roller

31

and then the tube pump

10

is driven by the gear

32

. A gear

35

for meshing with the gear

32

via an idler

34

is placed on a drive shaft

33

of the tube pump

10

.

A cleaner cam

38

having an arm

37

pressed by a spring

36

placed on the rear of the drive shaft

33

for frictional rotation is idly rotatably attached to the drive shaft

33

. As the cleaner cam

38

(arm

37

) is rotated, a wiping member

39

(wiping device

11

) can be moved in the horizontal direction. Accordingly, as the motor turns in one direction, the wiping device

11

can advance to the move path of the recording head

12

and can wipe the nozzle formation face of the recording head

12

and as the motor turns in an opposite direction, the wiping device

11

is retreated from the move path of the recording head

12

.

A ratchet wheel

40

, an intermediate transmission wheel

41

, and a pump wheel

42

are placed on the drive shaft

33

of the tube pump

10

so that they are stacked on each other in the axial direction. The ratchet wheel

40

is formed with a projection

40

a

on the face opposed to the intermediate transmission wheel

41

and the intermediate transmission wheel

41

is formed on both faces with projections

41

a

and

41

b

. Further, the pump wheel

42

is formed with a projection

42

C on the face opposed to the intermediate transmission wheel

41

.

Accordingly, the ratchet

40

rotates and the projection

40

a

thereof abuts the projection

41

a

of the intermediate transmission wheel

41

, whereby the rotation force is transmitted to the intermediate transmission wheel

41

. Further, the projection

41

b

of the intermediate transmission wheel

41

abuts the projection

42

C of the pump wheel

42

, whereby the rotation force is transmitted to the pump wheel

42

. Therefore, a rotation delay mechanism is formed for generating a rotation transmission delay at the maximum of about two revolutions between the ratchet wheel

41

and the pump wheel

42

if the turn direction of the paper feed motor

23

is switched.

When record paper

6

is fed from the cut sheet feeder, the paper feed motor

23

needs to be a little forward and reversely turned to position the paper tip and eliminate a backlash, in which case the rotation delay mechanism operates so that power is not transmitted to the tube pump

10

.

Next, a tube pump according to a first embedment of the invention will be discussed in detail with reference to

FIGS. 3

to

5

.

FIG. 3

is a plan view to show the main part of the tube pump incorporating the invention.

FIG. 4

is a plan view to describe a roller support groove (groove wall) of a pump wheel in the tube pump incorporating the invention.

FIG. 5

is a side view to show a roller between the pump wheel and a roller guide in the tube pump incorporating the invention. Members (parts) identical with or similar to those previously described with reference to

FIGS. 7 and 8

are denoted by the same reference numerals in

FIGS. 3

to

5

and will not be discussed again in detail.

A pump frame

44

(shown in

FIGS. 7 and 8

) has a tube support face

52

such that the contact area between a flexible tube

51

and a roller

43

a

is provided substantially all around the circumference of the pump wheel

42

(namely 360 degrees), as shown in FIG.

3

.

A pump wheel

42

shown in

FIGS. 3

to

5

is switched between pump operation and release operation as it rotates in either of the two different rotation directions.

The pump operation refers to operation wherein as the pump wheel

42

rotates in one direction, the roller

43

a

leans to the outer peripheral portion of the wheel and pressurizes the flexible tube

51

between the roller

43

a

and the tube support face

52

for producing suction operation. On the other hand, the release operation refers to operation wherein as the pump wheel

42

rotates in an opposite direction, the roller

43

a

leans to the wheel center portion of the pump wheel

42

and does not pressurize the flexible tube

51

.

The pump wheel

42

is formed with a single roller support groove

42

a

at a position eccentric from the wheel center (rotation center) and opened to both end faces of the wheel. Each opening of the roller support groove

42

a

is formed with such a gradient crossing the wheel diameter direction between the wheel center portion and the wheel peripheral portion. As shown in

FIGS. 3 and 4

, a groove wall

42

A of the roller support groove

42

a

is formed by such a cam face wherein the roller

43

a

rotates and rolls and is displaced from release operation position a to pump operation position b with rotation of the pump wheel

42

in pump operation direction A from the release operation state and wherein the roller

43

a

stops rotating and rolling and is displaced from the pump operation position b to the release operation position a with rotation of the pump wheel

42

in release operation direction B from the pump operation state.

Thus, the cam curve of the groove wall (cam face)

42

A in the roller support groove

42

a

is a curve with an arbitrary point on a line represented by polar coordinates (r, θ) wherein the rotation center of the pump wheel

42

is origin O, radius r (mm) is a function of angle θ (radians) found from r=C

1

×exp (α·θ) , and end angle θ

β

(start angle θ=θ

0

=0) is a constant found from θ

β

=(1/α)×log (C

2

/C

1

).

However, polar coordinates (r, θ) of both end points a (release operation position) and b (pump operation position) on the cam curve are set to predetermined polar coordinates (C

1

=6.530, 0) and (C

2

=7.950, θ

β

). Pressure angle α (radians) of the groove wall

42

A with respect to the roller shaft

43

A is set to α=7π/180 (7°).

The pressure angle α is the angle resulting from subtracting angle π/2 from the angle between line A

1

, A

2

, A

3

, . . . , A

19

connecting the rotation center O of the pump wheel

42

and arbitrary point a

1

, a

2

, a

3

, . . . , a

19

and tangent B

1

, B

2

, B

3

, . . . , B

19

to the cam curve at a

1

, a

2

, a

3

, . . . , a

19

on the line A

1

, A

2

, A

3

, . . . , A

19

, as shown in FIG.

4

.

If the pressure angle α (radians) is set to α=7π/180 (7°) and the polar coordinates (r, θ) of both end points a and b on the cam curve are set to (6.530, 0) and (7.950, θ

β

), the end angle θ

β

becomes θ

β

=π/2 and thus the polar coordinates (r, θ) of the arbitrary points a

1

, a

2

, a

3

, . . . , a

19

on the cam curve of the roller support groove

42

a

become as shown under the column of pressure angle α=7° in Table 1. In the table, the polar coordinates (r, θ) of the arbitrary points a

5

and a

12

on the cam curve become (6.822, π/9) and (7.364, 55π/180).

In the table, r (radius) is in mm units and θ, α (angle) is in ° (degree) units

TABLE 1

PRESSURE

ANGLE (α = 6°)

RAD-

(α = 7°)

(α = 8°)

(α = 9°)

ANGLE(θ)

IUS(r)

(θ)

(r)

(θ)

(r)

(θ)

(r)

α

1

0

6.530

0

6.530

0

6.530

0

6.530

α

2

5

6.589

5

6.602

6

6.611

5

6.622

α

3

10

6.648

10

6.674

10

6.693

10

6.716

α

4

15

6.708

15

6.748

15

6.775

15

6.811

α

5

20

6.768

20

6.822

20

6.859

20

6.908

α

6

25

6.829

25

6.897

25

6.944

25

7.005

α

7

30

6.890

30

6.973

30

7.030

30

7.105

α

8

35

6.952

35

7.049

35

7.117

35

7.205

α

9

40

7.014

40

7.127

40

7.205

40

7.307

α

10

45

7.077

45

7.205

45

7.294

45

7.411

α

11

50

7.141

50

7.284

50

7.385

50

7.515

α

12

55

7.205

55

7.364

55

7.476

55

7.622

α

13

60

7.270

60

7.445

60

7.568

60

7.730

α

14

65

7.335

65

7.527

65

7.662

65

7.839

α

15

70

7.401

70

7.610

70

7.757

70

7.950

α

16

75

7.468

75

7.694

75

7.853

—

—

α

17

80

7.535

80

7.778

80

7.950

—

—

α

18

85

7.602

85

7.864

—

—

—

—

α

19

90

7.671

90

7.950

—

—

—

—

α

20

95

7.740

—

—

—

—

—

—

α

21

100

7.809

—

—

—

—

—

—

α

22

105

7.879

—

—

—

—

—

—

α

23

110

7.950

—

—

—

—

—

—

At the axial end part of the pump wheel

42

, a roller guide

55

is provided integrally via a joint part

56

, as shown in FIG.

5

. The roller guide

55

is formed in a side face portion with a guide face

55

a

for guiding the roller shaft

43

A together with the groove wall

42

A of the roller support groove

42

a

. The guide face

55

a

is formed by a cam face similar to that of the groove wall

42

A of the roller support groove

42

a.

Since the tube pump is thus configured, when the release operation state is switched to the pump operation state, the roller

43

a

rotates and rolls and receives such a force displacing from the release operation position a to the pump operation position b from the groove wall

42

A of the roller support groove

42

a

(the guide face

55

a

of the roller guide

55

).

On the other hand, when the pump operation state is switched to the release operation state, the roller

43

a

remains immobile and receives such a force displacing from the pump operation position b to the release operation position a from the groove wall

42

A of the roller support groove

42

a.

Therefore, in the embodiment, just after the pump operation state is switched to the release operation state, the roller

43

a

is prevented from rotating and rolling in the wheel rotation direction while pressing the flexible tube

51

, so that fluids of ink, air, etc., in the flexible tube

51

do not flow back and the reliability on the pump quality can be enhanced.

In the embodiment, the case where the pressure angle α is set to α=7π/180 (7°) has been described, but the invention is not limited to it and if the pressure angle α is set to α=8π/180 (8°), a similar advantage to that of the embodiment can be provided.

In this case, if the polar coordinates (r, θ) of both end points a and b on the cam curve are set to (6.530, 0) and (7.950, θ

β

) as in the embodiment, the end angle θ

β

becomes θ

β

=4π/9. Accordingly, the polar coordinates (r, θ) of the arbitrary points a

1

, a

2

, a

3

, . . . , a

17

on the cam curve of the roller support groove

42

a

become as shown under the column of pressure angle α=8° in Table 1. In the table, for example, the polar coordinates (r, θ) of the arbitrary points a

3

and a

15

on the cam curve become (6.693, π/18) and (7.757, 7π/180).

However, if the pressure angle α is set to α=π/30 (6°) or π/20 (9°) (Table 1 lists the polar coordinates of arbitrary points a

1

, a

2

, a

3

, . . . , a

23

and a

1

, a

2

, a

3

, . . . , a

15

on the cam curve of the roller support groove

42

a

), the advantage as shown in the embodiment cannot be provided.

That is, if the pressure angle α is set to α=π/30, when the pump operation state is switched to the release operation state, the roller

43

a

does not move toward the release operation position and moves interlockingly with the pump wheel

42

while pressing the flexible tube

51

at an intermediate position in the roller support groove

42

a

. On the other hand, if the pressure angle α is set to α=π/20 (9°), when the release operation state is switched to the pump operation state, the roller

43

a

does not move toward the pump operation position b and moves interlockingly with the pump wheel

42

.

Thus, it is desirable that the pressure angle α of the groove wall (cam face)

42

A in the roller support groove

42

a

should be set to a predetermined angle in the range of π/30<α (radians)<π/20.

In addition, in the embodiment, the contact area between the roller

43

a

and the flexible tube

51

is provided as the contact area substantially all around the circumference of the pump holder

42

(almost 360 degrees), so that the contact area becomes long in the circumferential direction and a higher negative pressure can be provided as compared with the related art example (wherein the contact area is almost half of the circumference of the wheel, shown in FIGS.

7

and

8

).

In the embodiment, the contact area between the roller

43

a

and the flexible tube

51

is provided as the contact area almost all around the circumference of the roller

43

a

, so that at the wheel rotation time, the roller shaft

43

A can be guided in the opposite direction to the rotation direction of the pump wheel

42

and thus the guide member (shown in

FIGS. 7 and 8

) formerly required becomes unnecessary.

Further, in the embodiment, the number of rollers

43

a

is one, so that the number of parts and the number of assembling steps can also be decreased.

On the other hand, to use the tube pump

10

in the embodiment with the ink jet recording apparatus, fluids of ink, air, etc., sucked from the recording head

12

can be prevented from flowing back into the capping device

9

.

Therefore, ink bubbles produced as in the related art are not produced, so that destroying of meniscuses as ink bubbles are broken can be prevented.

Thus, the normal ejection operation of ink droplets through the nozzle openings can be accomplished, so that a print fault called missing dots does not occur and the reliability on cleaning can be enhanced.

Next, a second embodiment of the invention will be discussed with reference to FIG.

6

.

FIG. 6

is a plan view to show the main part of a tube pump according to the second embodiment of the invention. Members identical with those previously described with reference to

FIGS. 3

to

5

are denoted by the same reference numerals in FIG.

6

and will not be discussed again in detail.

A pump wheel

42

shown in

FIG. 6

is formed with a pair of roller support grooves

42

a

and

42

b

positioned at parts symmetrical with respect to a point about the wheel center (rotation center) and opened to both end faces of the wheel. One roller support groove

42

a

is the same as that previously described in the first embodiment and therefore the other roller support groove

42

b

will be discussed. As with the roller support groove

42

a

, each opening of the roller support groove

42

b

is formed with such a gradient crossing the wheel diameter direction between the wheel center portion and the wheel peripheral portion.

A groove wall

42

B of the roller support groove

42

b

is formed by such a cam face wherein the roller

43

b

rotates and rolls and is displaced from release operation position a to pump operation position b with rotation of the pump wheel

42

in a pump operation direction from the release operation state and wherein the rollers

43

a

and

43

b

stop rotating and rolling and is displaced from the pump operation position b to the release operation position a with rotation of the pump wheel

42

in a release operation direction from the pump operation state.

Thus, the cam curve of the groove wall (cam face)

42

B in the roller support groove

42

b

, like the cam curve of the groove wall

42

A in the roller support groove

42

a

, is also a curve with an arbitrary point on a line represented by polar coordinates (r, θ) wherein the rotation center of the pump wheel

42

is origin O, radius r (mm) is a function of angle θ (radians) found from r=C

1

×exp (α·θ), and end angle θ

β

(start angle θ=θ

0

=0) is a constant found from θ

β

=(1/α)×log (C

2

/C

1

).

However, polar coordinates (r, θ) of both end points a (release operation position) and b (pump operation position) on the cam curve are set to predetermined polar coordinates (C

1

=6.530, 0) and (C

2

=7.950, θ

β

). Pressure angle α (radians) of the groove wall

42

B with respect to the roller shaft

43

B is set to a predetermined angle in the range of π/30<α (radians)<π/20.

Since the tube pump is thus configured, when the release operation state is switched to the pump operation state, the rollers

43

a

and

43

b

rotate and roll and receive such a force displacing from the release operation position a to the pump operation position b from the groove walls

42

A and

42

B of the roller support grooves

42

a

and

42

b.

On the other hand, when the pump operation state is switched to the release operation state, the rollers

43

a

and

43

b

remain immobile and receive such a force displacing from the pump operation position b to the release operation position a from the groove walls

42

A and

42

B of the roller support grooves

42

a

and

42

b.

Therefore, in the embodiment, just after the pump operation state is switched to the release operation state, the rollers

43

a

and

43

b

are prevented from rotating and rolling in the wheel rotation direction while pressing a flexible tube

51

, so that fluids of ink, air, etc., in the flexible tube

51

do not flow back and the reliability on the pump quality can be enhanced as in the first embodiment.

In the second embodiment, the contact area between the rollers

43

a

and

43

b

and the flexible tube

51

is provided in the area almost all around the pump wheel

42

. Thus, as with the first embodiment, a high negative pressure can be provided and the guide member (shown in

FIGS. 7 and 8

) becomes unnecessary as compared with the related art example.

On the other hand, to use the tube pump

10

in the embodiment with the ink jet recording apparatus, fluids of ink, air, etc., sucked from the recording head

12

can be prevented from flowing back into the capping device

9

, so that a print fault called missing dots can be prevented from occurring and the reliability on cleaning can be enhanced as in the first embodiment.

In the described embodiments, the tube support face

52

is the tube support face such that the contact area between the flexible tube

51

and the roller becomes almost all around the circumference of the pump wheel

42

, however the invention is not limited to it. The invention can also be applied to the cases where the tube support face

52

is the tube support face such that the contact area is provided on a half of the circumference of the pump wheel.

In the embodiment, the case where the paper feed motor is used as the drive source of the tube pump

10

and is also used as the drive source of the paper feed and ejection mechanism has been described, but the invention is not limited to it and separate drive sources may be provided for the tube pump

10

and the paper feed and ejection mechanism, of course.

As seen in the description made above, according to the tube pump according to the invention, the reliability on the pump quality can be enhanced and the whole structure can be simplified and costs can be reduced.

To use the tube pump according to the invention as a pump unit of the ink jet recording apparatus, the reliability on cleaning can be enhanced.

Number	Name	Date	Kind
4142845	Lepp et al.	Mar 1979	A
5586873	Novak et al.	Dec 1996	A
6082977	Nishioka	Jul 2000	A
6164767	Nakamura et al.	Dec 2000	A
6203295	Nishioka	Mar 2001	B1

Tube pump and ink jet recording apparatus using the tube pump

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)

Parent Case Info

US Referenced Citations (5)