Printing device

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a printing device capable of ejecting a liquid mixture composed, for example, of ink and a diluent toward a recording medium, and more particularly to an improvement in arrangement of nozzles.

2. Description of the Related Art

So-called on-demand-type ink jet printer is adapted to form print images on a recording medium such as paper or film by ejecting ink droplets through nozzles in response to recording signals supplied to the printer. Recently, the ink jet printer of such a on-demand type has been rapidly prevailed due to its compactness or low manufacturing cost.

U.S. Pat. No. 5,371,529 previously filed by the present applicant, discloses the printer of such an on-demand type in which a gradation of recorded images is achieved by mixing ink and a transparent solvent as diluent at adequate proportions with each other immediately before ejection thereof. In such a printer, a concentration of the print images can be varied every recording dot, so that the printer is advantageous for obtaining a high quality duplicate of natural images such as photographs.

The printer is of a so-called intermixing type in which ink and diluent are mixed together in an interior of the ejection nozzle.

Meanwhile, in the conventional intermixing type printing device, there has been a problem that undesired mixing of ink and diluent and, therefore, mutual diffusion proposed, in the afore-mentioned U.S. Pat. No. 5,371,529, the printer in which a one-way valve manufactured according to an electroforming method is disposed in a boundary region between ink and diluent so as to prevent occurrence of the mutual diffusion therebetween during the stand-by period.

However, it is often difficult to completely separate ink from diluent during the standby period only by the arrangement of such a one-way valve. In addition, The one-way valve has another problem that its manufacturing cost is high.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the afore-mentioned problems. It is therefore an object of the present invention to provide a printing device having a simple structure and capable of preventing the occurrence of undesired mixing of ink and diluent during a stand-by period of an ink ejection process whereby mixing of ink and diluent and ejection of a fluid mixture composed of the ink and the diluent can be carried out surely.

In a first aspect of the present invention, there is provided a printing device including an ejecting nozzle with a first discharge opening and a metering nozzle with a second discharge opening, which are provided separately from each other to feed two kinds of fluids through the first and second discharge openings, respectively, the two kinds of fluids being mixed together to form a fluid mixture to be ejected toward a recording medium, wherein a smallest distance d between a closest point on each of the respective first and second discharge openings of the metering and ejecting nozzles is in the range of 0≦d≦5 (SI) where SI stands for an opening area of the first discharge opening of the ejecting nozzle.

In a second aspect of the present invention, there is provided a printing device including an ejecting nozzle having a first discharge opening and a plurality of metering nozzles each having a second discharge opening, which are provided separately from each other to feed fluids through the first and second discharge openings, the fluids being mixed together to form a fluid mixture to be ejected toward a recording medium, wherein a minimum distance d between the first discharge opening of the ejecting nozzle and the second discharge opening of each of metering nozzles is in the range of 0≦d≦5· (SI) where SI stands for an opening area of the first discharge opening of the ejecting nozzle.

These and other objects, features and advantages of the present invention will become more apparently from the following detailed description when read in conjunction with the accompanying drawings and the appended claims.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is made to a detailed description to be read in conjunction with the accompanying drawings in which:

FIG. 1

is an enlarged sectional view showing a printing device according to a first embodiment of the present invention;

FIG. 2

is an enlarged plan view of the printing device shown in

FIG. 1

;

FIGS. 3A

,

3

B and

3

C are enlarged plan views showing various modifications concerning shapes of discharge openings of ejecting and metering nozzles;

FIGS. 4A

,

4

B,

4

C,

4

D and

4

E are enlarged sectional views showing a sequence of mixing and ejecting operations of the printing device according to the first embodiment of the present invention;

FIG. 5

is an enlarged sectional view showing a printing device according to a second embodiment of the present invention;

FIG. 6

is an enlarged plan view of the printing device shown in

FIG. 5

;

FIG. 7

is an enlarged sectional view showing a printing device according to a third embodiment of the present invention;

FIG. 8

is an enlarged plan view of the printing device shown in

FIG. 5

;

FIGS. 9A

to

9

C are views showing a printing device according to a fourth embodiment of the present invention;

FIG. 9A

is a plan view showing the condition in which a cover plate is removed therefrom,

FIG. 9B

is a front elevation of the printing device when viewed from a nozzle side thereof, and

FIG. 9C

is a vertical section of the printing device;

FIG. 10

is a plan view showing a base plate of a printing device according to a fifth embodiment of the present invention;

FIG. 11

is a front elevation of the printing device shown in

FIG. 10

;

FIG. 12

is a plan view showing a base plate of a printing device according to a sixth embodiment of the present invention;

FIG. 13

is a front elevation of the printing device shown in

FIG. 12

;

FIG. 14

is a rear view of the base plate shown in

FIG. 12

;

FIG. 15

is a plan view showing a base plate of a printing devise according to a seventh embodiment of the present invention;

FIG. 16

is a front elevation of the printing device shown in

FIG. 15

; and

FIG. 17

is a rear view of the base plate shown in FIG.

15

;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a printing device according to the present invention are described in detail below by referring to the accompanying drawings. Incidentally, as will be clearly appreciated, the printing device described in the respective embodiments is provided with an ejecting nozzle and a metering nozzle separately. In the printing device according to the present invention, ink and diluent are mixed together at an exterior of the ejecting nozzle. Such a printing device is hereinafter referred to as “non-premixing-type printing device.”

Embodiment 1

In this embodiment, there is illustrated a so-called nonpre-mixing-type printing device in which discharge openings of ejecting and metering nozzles are located separately in the same plane and a passage of the metering nozzle is inclined relative to that of the ejecting nozzle.

As shown in

FIGS. 1 and 2

, such a printing device has an orifice plate in which the ejecting nozzle

1

and the metering nozzle

2

are separately provided. The orifice plate

3

may be a plate-like or film-like member made of metal such as nickel or stainless steel, a ceramic material such as glass or silicon, or a plastic material such as polyimide or polyethylene terephthalete.

The ejecting nozzle

1

provided in the orifice plate

3

is in the form of a straight through hole extending in the direction of a thickness of the orifice plate

3

. The ejecting nozzle

1

is provided, at one end thereof, with a discharge opening la and, at the other end, with a supply opening lb. To the supply opening lb, a transparent solvent

4

, for example, a diluent is supplied through a diluent feed passage

5

.

On the other hand, the metering nozzle

2

is also in the form of a through hole and defines a flow path inclined relative to the diluent feed passage

5

which communicates with the ejecting nozzle

1

. That is, the metering nozzle

2

is provided at one end thereof with a discharge opening

2

a

serving as an ink orifice. The inclination of the metering nozzle

2

relative to the ejecting nozzle

1

is such that the former gradually approaches the latter from a back side of the orifice plate

3

toward a front side thereof at which the discharge opening

2

a

is located. The inclined flow path of the metering nozzle

2

is formed, for example, by a laser-machining process.

In order to produce the metering nozzle

2

inclined relative to the ejecting nozzle

1

, the orifice plate

3

, which is made of a polyimide film having a thickness of 50μm, is radiated with a excimer-laser beam at an angle of 43 degrees relative to a normal line of the orifice plate

3

, though the inclination angle of the metering nozzle is not particularly limited.

The metering nozzle

2

is provided at the opposite end with a supply opening

2

b

to which a fluid, for example, ink

6

, is supplied through an ink-feeding passage

7

.

It is desirable that the discharge opening

1

a

of the ejecting nozzle

1

is of a point-symmetrical shape in section from a standpoint of achieving the function to eject fluid droplets. In addition, in view of easiness in designing or production, the discharge opening la is preferably of a circular or square shape in section. In this embodiment, the discharge opening of a circular shape is adopted.

On the other hand, the metering nozzle

2

has a large degree of freedom with respect to the shape of the discharge opening

2

a

. The shape of the discharge opening

2

a

is not limited to a circular shape but any shape such as, for example, an ellipsoidal shape, a triangular shape or a crescent shape as shown in

FIGS. 3A

to

3

C is applicable. The discharge opening

2

a

having any of these shapes can be easily formed by varying the shape of a mask used in a laser-machining process. For example, an intended shape of the discharge opening

2

a

is a circle, it can be formed by using a mask having an ellipsoidal shape.

Especially, in this embodiment, in order to prevent natural mixing of the ink

6

and the transparent solvent

4

during the stand-by period, the metering nozzle

2

and the ejecting nozzle

1

are separately disposed and a smallest distance d between a closest point on the discharge opening

1

a

of the ejecting nozzle

1

and a closest point on the discharge opening

2

a

of the metering nozzle

2

is limited to the range of 0≦d≦5 (S

1

), preferably 0≦d≦5 m where S

1

stands for an opening area of the discharge opening

1

a

of the ejecting nozzle

1

. If the smallest distance d exceeds 5 (S

1

), there is a possibility that a responsibility for accurately determining an amount of ink is deteriorated.

The opening area S

1

of the discharge opening

1

a

of the ejecting nozzle

1

is preferably in the range of 50≦S

1

≦40,000μm

2

, more preferably 100≦S

1

≦10,000 m

2

. The upper limit of the opening area S

1

is determined so as to obtain print images having a minimum resolution required. For example, the minimum resolution required is 75 dpi at 40,000m

2

and 200 dpi at about 10,000m

2

. Accordingly, when the opening area S

1

exceeds 40,000m

2

, print images having the minimum resolution cannot be obtained. On the other hand, when the lower limit of the opening area S

1

is determined so as to assure the discharge of fluid mixture through the ejecting nozzle. When the opening area S

1

is less than 50m

2

, the fluid mixture cannot be ejected through the ejecting nozzle.

The opening area S

2

of the discharge opening

2

a

of the metering nozzle

2

is preferably in the range satisfying the condition of {fraction (5/10,000)}≦S

2

/S

1

≦10. When the ratio S

2

/S

1

of the opening area S

2

to the opening area S

2

exceeds 10, ink spreads over an area surrounding the discharge opening so that an accuracy for metering the ink is deteriorated. On the other hand, when the ratio S

2

/S

1

is less than {fraction (5/10,000)}, the amount of ink to be metered at one metering cycle becomes too small. In addition, in order to perform the metering of ink with a high accuracy, the afore-mentioned opening area S

2

is in the range satisfying the condition of {fraction (5/10,000)}≦S

2

/S

1

≦5. Furthermore, in order to accomplish the high-accuracy metering of ink only at one metering cycle, the ratio S

2

/S

1

is preferably in the range of {fraction (1/100)}≦S

2

/S

1

≦5. When it is required to reduce a minimum concentration of dots recorded, the ratio S

2

/S

1

is preferably in the range of {fraction (1/100)}≦S

2

/S

1

≦½.

Next, recording operation of the printing device according to the present invention is described by referring to

FIGS. 4A

to

4

E.

When the printing device is in a stand-by condition, the transparent solvent

4

and ink

6

form a meniscus

8

at the discharge opening la of the ejecting nozzle

1

and a meniscus

9

at the discharge opening

2

a

of the metering nozzle

2

, respectively, due to a surface tension thereof, as shown in FIG.

4

A.

In the printing device according to the present invention, since the metering nozzle

2

and the ejecting side nozzle

1

are independently provided and the smallest distance d there-between each respective closest point is limited to the afore-mentioned range, natural mixing of the transparent solvent

4

and the ink

6

in the stand-by condition can be surely prevented without provision of complicated mechanisms such as one-way valve.

Next, the manner that the ink

6

metered is contacted and mixed with the transparent solvent, is explained. An inner pressure of the metering nozzle

2

is raised by operating a pressure-applying means (not shown) such as a piezoelectric element or a heating element, so that the ink

6

is metered as shown in FIG.

4

B. The amount of the ink

6

to be mixed with the transparent solvent

4

is varied by controlling a voltage value of voltage pulse or a pulse width impressed on the pressure-applying means.

At this time, since the flow path of the metering nozzle

2

is inclined relative to the ejecting nozzle

1

, the ink

6

emerges from the discharge opening

2

a

of the metering nozzle

2

toward the discharge opening la of the ejecting nozzle

1

, so that the ink

6

is allowed to be contacted and mixed with the transparent solvent

4

due to an effect of surface tension.

Thereafter, the application of voltage to the pressure-applying means provided on the metering side is interrupted, and a driving pulse is applied to another pressure-applying means provided on the ejecting side, so that the inner pressure in the ejecting nozzle

2

is lowered to a negative pressure while the inner pressure in the ejecting nozzle is raised. As a result, the ink

6

is separated from the fluid mixture

10

composed of the ink

6

and the transparent solvent

4

and returned into the metering nozzle

2

so that the meniscus of the ink

6

is retracted to a position inside the metering nozzle

2

, as shown in FIG.

4

C. On the other hand, the fluid mixture separated from the ink

6

projects outwardly from the discharge opening la of the ejecting nozzle

1

, as shown in FIG.

4

C.

Successively, when the driving pulse applied to the pressure-applying means on the ejecting side is interrupted, the inner pressure in the ejecting nozzle

1

is reduced to a negative pressure. As a result, as shown in

FIG. 4D

, the transparent solvent

4

is retracted into an interior of the ejecting nozzle

1

so that the fluid mixture

10

having a given ink concentration is ejected in the form of droplets.

After completion of the ink ejection, as shown in

FIG. 4E

, the metering nozzle

2

is charged with a fresh amount of ink

6

whereby the printer is returned to the initial stand-by condition.

Embodiment 2

This embodiment shows a printing device which is of the same non-premixing type as that of the Embodiment 1 but in which discharge openings of ejecting and metering nozzles are not located on the same plane.

As shown in

FIGS. 5 and 6

, such a printing device also includes an orifice plate

13

in which an ejecting nozzle

11

and a metering nozzle

12

are provided separately from each other. The ejecting nozzle

11

is in the form of a straight through-hole and penetrates the orifice plate

13

in the thickness direction in the same manner as the afore-mentioned Embodiment 1.

The ejecting nozzle

11

has, at one end thereof, a discharge opening

11

a

serving as a diluent orifice and, at the other end thereof, a supply opening

11

b

into which the transparent solvent

4

as a diluent is introduced through the diluent feed passage

5

.

On the other hand, the metering nozzle

12

is provided within a protrusion

14

projectingly formed on the orifice plate

13

. The protrusion

14

has a rectangular shape in front elevation and projects outwardly from a plane where the discharge opening

11

a

of the ejecting nozzle

11

is located. The metering nozzle

12

has such a configuration that a discharge opening

12

a

thereof is opened at a plane perpendicular to the plane where the discharge opening

11

a

of the ejecting nozzle

11

is located. This configuration makes it easier to mix the ink

6

with the transparent solvent

4

. The metering nozzle

12

further has, at the other open end, a supply opening

12

b

which communicates with a ink feed passage

7

for supplying the ink

6

to the metering nozzle

12

.

Incidentally, the orifice plate

13

may be provided thereon with multiple plated layers each made of nickel, copper or the like.

In the printing device of this embodiment, a smallest distance d between the closest point on discharge opening

11

a

of the ejecting nozzle

11

and the closest point on discharge opening

12

a

of the metering nozzle

12

is so determined as to fall within the same range as described in the afore-mentioned Embodiment 1. Similarly, an opening area SI of the discharge opening

11

a

of the ejecting nozzle

11

and an opening area SI of the discharge opening

12

a

of the metering nozzle

12

are so determined as to satisfy the same conditions as described in the afore-mentioned Embodiment 1. In addition, the discharge openings

11

a

and

12

a

of the ejecting and metering nozzles

11

and

12

can have various shapes as mentioned in Embodiment 1.

The printing device of this embodiment can be operated in the same manner as described in Embodiment 1.

Embodiment 3

This embodiment illustrates a printing device which is of the same non-premixing type as that of the Embodiment 1 but in which discharge openings of ejecting and metering nozzles are not located on the same plane. In this embodiment, the metering nozzle is also arranged in an inclined relation to the ejecting nozzle.

As shown in

FIGS. 7 and 8

, such a printing device also includes an orifice plate

17

in which an ejecting nozzle

15

and a metering nozzle

16

are provided separately from each other. The ejecting nozzle

15

is in the form of a straight through-hole and extends through the orifice plate

17

in the direction of a thickness thereof in the same manner as the afore-mentioned Embodiment 1.

The ejecting nozzle

15

has, at one end thereof, a discharge opening

15

a

serving as a diluent orifice and, at the other end thereof, a supply opening

15

b

into which the transparent solvent

4

as a diluent is introduced through the diluent feed passage

5

in the same manner as described in the afore-mentioned Embodiment 1.

On the other hand, the metering nozzle

16

is provided in an enlarged portion of the orifice plate

17

which has a larger thickness than that of a portion where the ejecting nozzle

15

is located. The metering nozzle

16

is also inclined toward the ejecting nozzle

15

to make it easier to mix the ink

6

with the transparent solvent

4

. A discharge opening

16

a

of the metering nozzle

16

is opened at a slant surface

18

provided on the enlarged portion of the orifice plate

17

. The metering nozzle

16

is provided, at the other end, a supply opening

16

b

which communicates with the ink feed passage

7

to introduce the ink

6

into the metering nozzle

16

.

Incidentally, the orifice plate

17

can be produced by subjecting a plastic sheet to a hole-forming process in which an excimer-laser is employed.

In the printing device of this embodiment, a smallest distance d between a closest point of the discharge opening

15

a

of the ejecting nozzle

15

and corresponding closest point on the discharge opening

16

a

of the metering nozzle

16

is so determined as to fall within the same range as described in the afore-mentioned Embodiment 1. Similarly, an opening area SI of the discharge opening

15

a

of the ejecting nozzle

15

and an opening area S

2

of the discharge opening

16

a

of the metering nozzle

16

are so determined as to satisfy the same conditions as described in the afore-mentioned Embodiment 1. In addition, the discharge openings

15

a

and

16

a

of the ejecting and metering nozzles

15

and

16

can have various shapes as mentioned in Embodiment 1.

The printing device of this embodiment can be also operated in the same manner as described in Embodiment 1.

Embodiment 4

In the afore-mentioned embodiments, there are described printing devices all having the orifice plate. However, the present invention is also applicable to printing devices having no orifice plate. Embodiment 4 shows a so-called end-face type printing device having no orifice plate.

In the production of such a printing device, as shown in

FIG. 9

, a primary surface of a base

19

made of stainless steel or the like is grooved by using etching or the like methods to form two channels thereon. The thus-formed two channels serving respectively as a metering nozzle

20

and an ejecting nozzle

21

is covered with a cover plate

22

adhered onto the primary surface of the base

19

. In this case, a smallest distance d between discharge openings of the metering nozzle

20

and the ejecting nozzle

21

is so determined as to satisfy the same conditions as described in Embodiment 1. Similarly, an opening area SI of the discharge opening of the ejecting nozzle

21

and an opening area S

2

of the discharge opening of the metering nozzle

20

are so determined as to satisfy the same conditions as described in the afore-mentioned Embodiment 1. In addition, the discharge openings of the ejecting and metering nozzles

21

and

20

can have various shapes as mentioned in Embodiment 1.

The printing device of this embodiment can be also operated in the same manner as described in Embodiment 1.

Embodiment 5

This embodiment shows a printing device which is a combination of the end-face type having no orifice plate, and the non-premixing type having a plurality of metering nozzles.

Such a printing device has substantially the same configuration as that of the printing device described in Embodiment 4.

That is, as shown in

FIGS. 10 and 11

, a primary surface

31

a

of a base plate

31

is grooved to form a first channel

34

which defines a diluent feed passage

32

for the transparent solvent as a diluent and an ejecting nozzle

33

communicated with the diluent feed passage

32

, a second channel

37

which defines a first ink feed passage

35

for the ink and a first metering nozzle

36

communicated with the first ink feed passage

35

, and a third channel

40

which defines a second ink feed passage

38

and a second metering nozzle

39

communicated with the second ink feed passage

38

. The first channel

34

is so arranged as to be interposed between the second and third channels

37

and

40

. The first to third channels are covered by a diaphragm

41

adhered onto the primary surface

31

a

of the base plate

31

to finally define the respective nozzles and passages.

Accordingly, similar to the preceding embodiments, the transparent solvent as a diluent is supplied through the diluent feed passage

32

to the ejecting nozzle

33

. Whereas, the ink is supplied through the first and second ink feed passages

35

and

38

to the first and second metering nozzles

36

and

39

, respectively.

The afore-mentioned channel

34

is in the form of a droplet when viewed in top plan and has a relatively wide portion serving as the diluent feed passage

32

and a relatively narrow portion serving as the ejecting nozzle

33

and gradually tapered in width toward an open end thereof.

The second and third channels

37

and

40

are also of a droplet shape in top plan and further inclined relative to the ejecting nozzle

33

in order to facilitate metering and emerging of the ink and mixing of the ink with the transparent solvent. The second and third channels

37

and

40

each have a relatively wide portion serving as the first or second ink feed passage

35

or

38

, and a relatively narrow portion serving as the first or second metering nozzle

36

or

39

and gradually tapered in width toward an open end thereof. As described above, since the first and second metering nozzles

36

and

39

constituted by the relatively narrow portions of the first and second channels

37

and

40

, respectively, are inclined relative to the ejecting nozzle

33

, the ejecting nozzle

33

is interposed between the first and second metering nozzles

36

and

39

such that the discharge openings of these nozzles are arranged adjacent to each other at one end face of the base plate

31

.

Meanwhile, the base plate

31

and the diaphragm

41

may be made of metal such as nickel and stainless steel, a ceramic material such as glass and silicon, or a plastic material such as polyimide and polyethylene terephthalate. The formation of the channels on the primary surface

31

a

of the base plate

31

can be performed by etching, injecting-molding or other adequate methods depending upon the kind of material used therefore.

In this embodiment, in order to prevent undesired mixing of the ink

6

and the transparent solvent

4

during the stand-by period, the first and second metering nozzle

36

and

39

and the ejecting nozzle

33

are separately disposed and a smallest distance d between a closest point of the discharge opening of the ejecting nozzle

33

and the closest point of the discharge opening of the first or second metering nozzle

36

or

39

is limited to the same range as described in the aforementioned Embodiment 1. Similarly, an opening area SI of the discharge opening of the ejecting nozzle

33

and an opening area S

2

of the discharge opening of the first or second metering nozzle

36

and

39

are so determined as to satisfy the same conditions as described in the afore-mentioned Embodiment 1. In addition, the discharge openings of the ejecting nozzle

33

and the first and second metering nozzles

36

and

39

may be of various shapes as mentioned in Embodiment 1.

In the printing device according to this embodiment, the diaphragm

41

is provided, at respective positions opposed to the diluent feed passage

32

and the first and second ink feed passages

35

and

38

, with laminate-type piezoelectric elements

42

,

43

and

44

as pressure-applying means.

Incidentally, the printing device according to this embodiment can be operated in substantially the same manner as described in Embodiment 1. That is, one medium supplied from the ejecting nozzle

33

is mixed with the other medium supplied from the first metering nozzle

36

and/or the second metering nozzle

39

and the resultant fluid mixture is ejected toward a recording medium such as paper.

In the printing device of this embodiment, when the first and second ink feed passages

35

and

38

are charged with ink having the same color tone and the same concentration, it is possible to supply a given amount of ink metered through either or both of the first and second metering nozzles. In such a construction, the fluid mixture having a high ink concentration can be ejected by supplying the metered ink through both the first and second metering nozzles. In general, if a pressure-applying means such as a piezoelectric element is employed under a high-power condition, there is a tendency that its responsibility to a pulse width of a supply voltage and the voltage level is deteriorated. Accordingly, if the formation of the fluid mixture having a high ink concentration is made by using a single metering nozzle, deterioration of the mixing accuracy is likely to occur. To the contrary, in the printing device according to the present embodiment, a given amount of ink metered is supplied from both the first and second metering nozzles

36

and

39

so that the deterioration of the mixing accuracy does not occur but it is rather improved, whereby print images with a high accuracy can be obtained.

In addition, in the printing device according to the present embodiment, when the first and second ink feed passages

35

and

38

can be charged with ink compositions having the same color tone but different ink concentrations, metering of ink in the fluid mixture to be ejected can be performed by selecting either one of the first and second metering nozzles

36

and

39

depending upon intended concentration of the fluid mixture. This permits a wider dynamic range of the concentration of the fluid mixture and a higher resolution of the print images recorded than those obtained in the conventional printing devices.

Furthermore, in the printing device according to the present invention, when the first and second ink feed passages

35

and

38

are charged with ink compositions having different color tones, two kinds of fluid mixtures each composed of diluent and either one of ink compositions having different color tones can be selectively ejected from the single nozzle unit. This enables reduction in total number of nozzles and size of the printing device. In this case, when the different ink compositions are supplied from the metering nozzles at the same time, it is possible to eject the fluid mixture having a mixed color tone.

Embodiment 6

This embodiment shows a printing device which is also a combination of the end-face type having no orifice plate, and the non-premixing type having a plurality of metering nozzles.

Such a printing device has substantially the same configuration as that of the printing device described in Embodiment 5.

That is, as shown in

FIGS. 12 and 13

, a primary surface

51

a

of a base plate

51

is grooved to form a first channel

54

which defines a diluent feed passage

52

for the transparent solvent as a diluent and an ejecting nozzle

53

communicated with the diluent feed passage

52

, a second channel

57

which defines a first ink feed passage

55

and a first metering nozzle

56

communicated with the first ink feed passage

55

, and a third channel

60

which defines a second ink feed passage

58

and a second metering nozzle

59

communicated with the second ink passage

58

. The first channel

54

is so arranged as to be interposed between the second and third channels

57

and

60

. The first to third channels are covered with a diaphragm

41

adhered onto the primary surface

51

a

of the base plate

51

to finally define the respective ink feed and diluent feed passages and the ejecting and metering nozzles.

In the printing device of this embodiment, as shown in

FIGS. 13 and 14

, the base plate

51

is further provided, on a back surface

51

b

thereof opposite to the primary surface

51

a

, with a third channel

64

which defines a third ink feed passage

62

and a third metering nozzle

63

communicated with the third ink feed passage

62

. The fourth channel

64

on the back surface

51

b

is disposed in an opposed relation to the first channel

54

on the primary surface

51

a

. The fourth channel

64

is covered with a diaphragm

65

to finally define the third ink feed passage

62

and the third metering nozzle

63

.

Similar to the preceding embodiments, in the printing device of this embodiment, the transparent solvent as a diluent is supplied through the diluent feed passage

52

to the ejecting nozzle

53

and the ink is supplied through the first, second and third ink feed passages

55

,

58

, and

62

to the discharge opening of the first, second and third metering nozzles

56

,

59

and

63

, respectively.

The first, second and third channels

54

,

57

and

60

may each have a similar shape to those of the first, second and third channels

34

,

37

and

40

of the afore-mentioned Embodiment 4, respectively. Similarly, the fourth channel may be of an approximately droplet shape in top plan and has a relatively wide portion which defines the third ink feed passage

62

and a relatively narrow portion which defines the third metering nozzle

63

. As a result, the ejecting nozzle

53

is so arranged as to be interposed between the first and second metering nozzles

56

and

59

and opposed to the third metering nozzle

63

in the direction of a thickness of the base plate

51

.

Meanwhile, the base plate

51

and the diaphragms

61

and

65

may be made of the same materials as those described in the preceding Embodiment 5. The formation of the channels on the primary and back surfaces of the base plate

51

can be also performed in the same manner as described in Embodiment 5.

In the printing device of this embodiment, in order to prevent undesired mixing of the ink

6

and the transparent solvent

4

during the stand-by period, the first, second and third metering nozzles

56

,

59

and

63

and the ejecting nozzle

53

are separately disposed and a smallest distance d between the discharge opening of the ejecting nozzle

53

and the discharge opening of each of the first, second and third metering nozzles

56

,

59

and

63

is limited to the same range as described in the afore-mentioned Embodiment 1. Similarly, an opening area SI of the discharge opening of the ejecting nozzle

53

and an opening area S

2

of the discharge opening of each of the first, second and third metering nozzles

56

,

59

and

63

are so determined as to satisfy the same conditions as described in the aforementioned Embodiment 1. In addition, the discharge openings of the ejecting nozzle

53

and the first, second and third metering nozzles

56

,

59

and

63

may be of various shapes as described above, though there is some limitation.

In the printing device according to this embodiment, the diaphragm

61

is provided, at respective positions opposed to the diluent feed passage

52

and the first and second ink feed passages

55

and

58

, with laminate-type piezoelectric elements

66

,

67

and

68

as pressure-applying means and the oscillation plate

65

is provided, on an outside surface thereof opposed to the third ink feed passages

62

, with laminate-type piezoelectric elements

69

as a pressure-applying means.

Incidentally, the printing device according to this embodiment can be operated in substantially the same manner as described in Embodiment 1. That is, one medium supplied from the ejecting nozzle

53

is mixed with the other medium supplied from at least one of the first, second and third metering nozzles

56

,

59

and

63

and the resultant fluid mixture is ejected toward a recording medium such as paper.

In the printing device of this embodiment, the first, second and third ink feed passages

55

,

58

, and

62

are charged with ink having the same color tone and the same concentration, it is possible to supply a given amount of ink metered through either or both of the first, second and third metering nozzles. Alternatively, the first, second and third ink feed passages

55

,

57

, and

62

can be charged with ink compositions which are the same in color tone thereof but different in concentration from each other. This permits attainment of the same effects as described in Embodiment 5.

In addition, in the printing device according to the present embodiment, if the first, second and third metering nozzles are respectively supplied with ink compositions having different color tones, e.g., yellow, magenta and cyan, fluid mixtures each composed of diluent and either one of ink compositions having different color tones can be selectively ejected from the single nozzle unit. This enables reduction in total number of nozzles and size of the printing device. In this case, when the different ink compositions are supplied from the metering nozzles at the same time, it is possible to eject the fluid mixture having various mixed color tones whereby a full-colored print images can be obtained.

Embodiment 7

This embodiment shows a printing device which is also a combination of the end-face type having no orifice plate, and the non-premixing type having a plurality of metering nozzles.

Such a printing device has substantially the same configuration as that of the printing device described in Embodiment 5.

That is, as shown in

FIGS. 15 and 16

, a primary surface

71

a

of a base plate

71

is grooved to form a first channel

74

which defines a diluent feed passage

72

for the transparent solvent as a diluent and an ejecting nozzle

73

communicated with the diluent feed passage

72

, a second channel

77

which defines a first ink feed passage

75

and a first metering nozzle

76

communicated with the first ink feed passage

75

, and a third channel

80

which defines a second ink feed passage

78

and a second metering nozzle

79

communicated with the second ink passage

78

. The first channel

74

is so arranged as to be interposed between the second and third channels

77

and

80

. The first to third channels are covered with a diaphragm

81

adhered onto the primary surface

71

a

of the base plate

71

to finally define the respective ink feed and diluent feed passages and the ejecting and metering nozzles.

In the printing device of this embodiment, as shown in

FIGS. 16 and 17

, the base plate

71

is further provided, on a back surface

71

b

thereof opposite to the primary surface

71

a

, with a fourth channel

84

which defines a third ink feed passage

82

and a third metering nozzle

83

communicated with the third ink feed passage

82

, and a fifth channel which defines a fourth ink feed passage

85

and a fourth metering nozzle

86

communicated with the third ink feed passage

85

. The fourth and fifth channels

84

and

87

on the back surface

71

b

are disposed in an opposed relation to the second and third channel

77

and

80

on the primary surface

71

a

, respectively. In addition, The fourth and fifth channels

84

and

87

are covered with an diaphragm

88

adhered to the back surface

71

b

of the base plate

71

to finally define the third and fourth ink feed passage

82

and

85

and the third and fourth metering nozzle

83

and

86

.

Similar to the preceding embodiments, in the printing device of this embodiment, the transparent solvent as a diluent is supplied through the diluent feed passage

72

to the ejecting nozzle

73

and the ink is supplied through the first, second, third and fourth ink feed passages

75

,

78

,

82

and

85

to discharge openings of the first, second, third and fourth metering nozzles

76

,

79

,

83

and

86

, respectively.

The first, second and third channels

74

,

77

and

80

may have similar shapes to those of the first, second and third channels

34

,

37

and

40

of the afore-mentioned Embodiment 5, respectively. The fourth and fifth channels

84

and

87

may have approximately droplet shapes in top plan which correspond respectively to the shapes of the second and third channels

77

and

80

and are each formed with a relatively wide portion which defines the third or fourth ink feed passage

82

or

85

and a relatively narrow portion which defines the third metering nozzle

83

or

86

.

As a result, the ejecting nozzle

73

is so arranged as to be interposed between the first and second metering nozzles

76

and

79

. Besides, the first and second metering nozzles

76

and

79

are so arranged as to be opposed to and aligned with the third and fourth metering nozzles

83

and

86

in the direction of a thickness of the base plate

71

.

Meanwhile, the base plate

71

and the diaphragms

81

and

88

may be made of the same materials as those used in the preceding Embodiment 5. The formation of the channels on the primary and back surfaces

71

a

and

71

b

of the base plate

71

can be performed in the same manner as described in Embodiment 5.

In the printing device of this embodiment, in order to prevent undesired mixing of the ink

6

and the transparent solvent

4

during the stand-by period, the first, second, third and fourth metering nozzles

76

,

79

,

83

and

86

and the ejecting nozzle

73

are independently disposed in a smallest distance d between a closest point of the discharge opening of the ejecting nozzle

73

and a closest point of the discharge opening of each of the first, second, third and fourth metering nozzles

76

,

79

,

83

and

86

is limited to the same range as described in the afore-mentioned Embodiment 1. Similarly, an opening area S

1

of the discharge opening of the ejecting nozzle

73

and an opening area S

2

of the discharge opening of each of the first, second, third and fourth metering nozzles

76

,

79

,

83

and

86

are so determined as to satisfy the same conditions as described in the afore-mentioned Embodiment 1. In addition, the discharge openings of the ejecting nozzle

73

and the first, second, third and fourth metering nozzles

76

,

79

,

83

and

86

may have various shapes as described in the preceding embodiments, though there is some limitation due to the fact that they must that they must be defined by the respective channels and the diaphragms

81

and

88

.

In the printing device according to this embodiment, laminate-type piezoelectric elements

89

,

90

and

91

as pressure applying means are provided on the diaphragm

81

at the respective positions corresponding to the diluent feed passage

72

and the first and second ink feed passages

75

and

78

. In addition, laminate-type piezoelectric elements

92

and

93

also serving as pressure-applying means are provided on the oscillation plate

88

at the respective positions corresponding to the third and fourth ink feed passages

82

and

85

.

Incidentally, the printing device according to this embodiment can be operated in substantially the same manner as described in Embodiment 1. That is, one medium supplied from the ejecting nozzle

73

is mixed with the other medium supplied from at least one of the first, second, third and fourth metering nozzles

76

,

79

,

83

and

86

and the resultant fluid mixture is ejected toward a recording medium such as paper.

In the printing device of this embodiment, the first, second, third and fourth ink feed passages

75

,

78

,

82

and

85

are charged with ink compositions having the same color tone and the same concentration. Alternatively, the first, second, third and fourth ink feed passages

75

,

78

,

82

and

85

can be charged with ink compositions having the same color tone but different concentrations. This permits attainment of the same effects as described in Embodiment 5.

In addition, in the printing device according to the present embodiment, if the first, second, third and fourth metering nozzles are respectively supplied with ink compositions having different color tones, e.g., yellow, magenta, cyan and black, various fluid mixtures, which are each composed of the diluent and either one of ink compositions having different color tones, can be selectively ejected from the single nozzle unit. This enables reduction in total number of nozzles and size of the printing device. In this case, when the different ink compositions are supplied from the metering nozzles at the same time at proper proportions, it is possible to eject the fluid mixture having various mixed color tone whereby full-colored print images can be obtained.

The afore-mentioned embodiments are only illustrative and therefore not intended to limit a scope of the present invention. As will be apparently understood, various changes and modifications can be made without departing from the spirit and scope of the present invention.

For instance, in almost all of the afore-mentioned embodiments, the ejecting nozzle and the metering nozzles are so arranged that center lines of the latter intersects that of the former. However, the present invention is not restricted to such a particular arrangement. For example, the center lines of the ejecting and metering nozzles can be disposed in skewed relation or parallel to each other.

As described above, in a printing device according to the present invention, since metering and ejecting nozzles are provided separately from each other, there is no likelihood that ink and a diluent therefor are mixed together in a stand-by condition of the printing device whereby it is surely prevented to cause undesired mixing of the ink and the diluent upon ejection of the fluid mixture. In addition, This enables simplified construction of the printing device and permits stable mixing and ejecting operations of the fluid mixture composed of the ink and the diluent without complicated mechanisms such as valves, which leads to simplification of manufacturing processes and reduction in its manufacturing cost.

Besides, in accordance with the present invention, since a smallest distance d between discharge openings of the metering and range, a good ejecting nozzles is limited to a particular range, a good metering responsibility to fluid to be metered can be obtained and improved mixing and ejecting operations for the fluid mixture composed of the ink and the diluent can be surely performed.

The present invention is subject to many variations, modifications and changes in detail. It is intended that all matter described throughout the specification and shown in the accompanying drawings be considered illustrative only. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.

Number	Name	Date
4017869	Meyer et al.	Apr 1977
4614953	Lapeyre	Sep 1986
4630076	Yoshimura	Dec 1986
4746935	Allen	May 1988
4860026	Matsumoto et al.	Aug 1989
5777636	Naganuma et al.	Jul 1998
5825379	Kagami	Oct 1998
5980014	Kagami	Nov 1999

Number	Date	Country
3501 905 A1	Dec 1985	DE
0 538 147 A3	Oct 1992	EP
404329151	Nov 1992	JP

	Number	Date	Country
Parent	08/729495	Oct 1996	US
Child	09/401866		US

	Number	Date	Country
Parent	08/631029	Apr 1996	US
Child	08/729495		US

Printing device

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)

SPECIFICATION

US Referenced Citations (8)

Foreign Referenced Citations (3)

Continuations (1)

Continuation in Parts (1)