CA2062711A1

CA2062711A1 - Ink-jet print head using electromagnetic pumping method

Info

Publication number: CA2062711A1
Application number: CA002062711A
Authority: CA
Inventors: Yoon-Soo Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1991-12-23
Filing date: 1992-03-10
Publication date: 1993-06-24
Also published as: IT1254832B; GB2262717A; FR2685251A1; KR930012307A; GB9206382D0; ITMI920648A0; ITMI920648A1

Abstract

ABSTRACT OF DISCLOSURE

An ink-jet print head of electromagnetic pumping for performing a continuous tonal expression easily in response to an input print signal and simple structure for ejecting an ink by an electromagnetic pumping. The ink jet print head includes a magnetic field generating means for generating a uniform magnetic field from a first space to a second space, and a pumping tube member having a plurality of pumping tubes having isolated first and second electrodes formed separately in a center of an insulation panel at regular intervals, being installed in a magnetic field, wherein the conductive ink is ejected from the pumping tube by applying a voltage to the first and second electrode.

Description

TITLE OF THE INVENTION

INK-JET PRINT HEAD USING ELECTROMAGNETIC PUMPING METHOD

FIELD OF THE INVENTION

This invention relates to a print head of ink-jet printer of drop-on-demand type, and more particularly to an ink-jet print head for ejecting ink by an electromagnetic force responding to an externally applied voltage.

TECHNICAL BACRGROUND OF THE INVENTION

In general, ink-jet recording technique is the method of reproducing certain visible pattern on recording media such as paper by a group of electronically controlled ink drops. In the ink-jet recording, ink drops from the nozzle (orifice) adhere to the printing media which faces the ink-nozzle, thereby resulting in visible pattern.

Although there are more than twenty ink-jet printing methods, most of the ink-jet printers can be categorized into either one of:

(1) Drop-on-Demand type (DOD) or (2) Continuous Ink-jet type, wherein among several different DOD-type ink-jet printing methods, most popular types of this category may be:

(A) Thermal Ink-jet or Bubble-jet or (B) Piezo-electric element type.

The heart of the thermal ink-jet (or bubble-jet) (A) is resistive heating element placed inside an ink-chamber. One face of the ink-chamber has a hole connected to an orifice which is a tiny hole through which ink drop is ejected toward the recording media. Enormous heat generated instantaneously from the heating element due to current flow through the heating element evaporates ink and the pressure from the ink vapor accelerates the ink inside the ink-chamber toward the orifice to form a high speed ink drop when it escapes from the orifice.
Ink-jet head of this type has complicated shape and has problem in reproducing continuous tone since the size of the ink-drop is hard to control.

- $nk-jet head of type (B) has piezo-electric crystal which vibrates in accordance with the voltage signal applied across the 206271~

crystal. The vibrating energy is transferred to the motion energy of the ink-drop to form ink-drops. The drawback of this type is that the rate of ink-drop formation is low (2-3 KHz) causing low printing speed.

Continuous steam of ink drop is formed in the type (2) by using ink pump and vibrating nozzle. The flight path of the ink drop is modified when it passes through a deflecting electrode following charging electrode. The rate of the ink-drop formation is high (lOOKHz or above) and it enables the reproduction of continuous tone. However, since the system is complicated, the system tends to be large and high in price. And, in addition, maintaining the stream of ink-drop steadily still remains as a problem.

~UIIIIaRY OF THE INVENTION

lS An object of this invention is to provide an electromagnetic pumping ink-jet print head capable of effective continuous tonal gradation of print image in response to an input print signal.

The other object of this invention is to provide an ink-jet print head with simpler structure for ejecting the ink by means of an electromagnetic pumping method.

According to the present invention, an ink jet print head of drop-on-demand type for ejecting a conductive ink by electromagnetic pumping is provided with a magnetic field 2062~11 generating means for generating a uniform magnetic field from afirst space to a second space, and a pumping tube member comprising a plurality of pumping tubes having isolated first and second electrodes formed separately in a center of an insulation S panel at regular intervals, being installed in a magnetic field, wherein the conductive ink is ejected from the pumping tube by applying a voltage to the first and second electrode.

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily enjoyed as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like members indicate the same or similar components, wherein:

Fig.l is an exploded view of an electromagnetic pumping ink-jet print head of this invention;
Figs.2A and 2B is a front and plan view of the print head as shown in Fig.1;
Figs.3A and 3B is a detailed and enlarged view of essential part of the exploded view as shown in Fig.1;
Fig.4 is a front view of an electromagnetic pumping tube; and Figs.5A and 5B are a graph of variation of tone responding to a time and applied voltage.

:

DETAILED DESCRIPTION OF PREFERRED EM~ODIMENT8 A pumping tube member incorporating a plurality of pumping tubes comprising an isolated first and second electrodes into its body at regular intervals is located in a electromagnetic space of a given and uniform magnetic field generated from a first space to a second space.

By applying a positive voltage to the first electrode and a negative voltage to the second electrode, a given amount of current flows from the first electrode to the second electrode.
By the current flow between the two electrodes, a conductive ink in the pumping tube is accelerated and ejected toward an exit side according to a Fleming's left-hand rule.

For a pumping tube of the pumping tube member, a shape of quadrangle tube is desirable, and the first and second electrodes are fitted or coated separately on a right and left inner wall of the quadrangle tube. The first and second electrodes are of good conductive metal and positioned to an axial direction.

By placing the pumping tube in an electromagnetic space where a uniform magnetic field is applied from the first space to the second space, the conductive ink of the pumping tube is ejected by applying a drive voltage to the electrodes of the pumping tubes.

With reference to Fig.l, an electromagnetic pumping ink-jet print head comprises a pumping tube member 24 comprising an insulation panel 12 and a plurality of pumping tubes 14 having a first and second electrodes 16, 18 installed in the center of the insulation panel 12 at regular intervals, and a first and second magnet panel 20, 22 installed on the top and bottom side of the pumping tube member 24 for applying a uniform magnetic field to it.

The insulation panel 12 is an insulating material of glass or silicon wafer, which is treated equivalently. The first and second electrodes 16, 18 are a positive electrode (+) and a negative electrode (-) respectively, and are of good conductive material.

The first and second electrodes 16, 18 are coated on an inner wall of right and left side of each pumping tube 14 by such lS a plating method.

With reference to Figs.2A and 2B, a magnetic pole of S, N
of the first and second magnet panel 20, 22 is arrayed from a top side to a bottom side in order, and each pumping tube 14 has a given height H and width L3.

With reference to Fig.3A, the insulator 12 of hexahedron having a given height N, length L and width L2 forms a tube 14 in a direction of length, and the first and second electrode 16, 18 i8 coated on a left and right inner side of the tube 14.

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Fig. 3B is showing a more detailed position of the first and second electrode 16, 18 in the insulation panel 12. Fig.4 i6 a front view of the tube 14 as shown in Fig.3A and for describing a principle of electromagnetic pumping. Fig.5A and 5B is a curve graph of tone of an electromagnetic pumping ink-jet print head and shows a correlation of an applied voltage V to the fi-st and second electrode 16, 18 and a time to be varied. A shape of the tube is illustrated as a quadrangle for convenience and simplifying a model in Fig.l to Fig.4.

For describing an operation, it is assumed that a uniform magnetic field is applied to the pumping tube member 24 by the first and second magnetic panel 20, 22, and each tube 14 is filled with an ink of conductive material.

When a given state of voltage V corresponding to a print signal is applied across the first electrode 16 and second electrode 18 of the pumping tube 14, current flows from the first electrode 16 (positive electrode +) to the second electrode 18(negative electrode -).

Assuming that a magnetic field strength of the pumping tube member 24 is B ( shown as a vector ~), current density per unit length from the first electrode 16 to the second electrode 18 is I (shown as a vector I), the conductive material in the pumping tube 14 experiences a force directed to the direction of axis by Fleming's left-hand rule. If the force directed to the direction S of axis is indicated as F (shown as a vector F), F is expressed as an equation:

F = L3 ` I x B.. (1) wherein L3 is an inner width of the pumping tube 14.

Assuming that the applied voltage between the two electrodes 16 and 18 of the pumping tube 14 is V, the current I in the equation (1) is expressed as:

I = R ~ (2) wherein R is the resistance.per unit length of a conductive material filled in the tube 14.

The resistance R of the equation (2) is expressed as:

' R-p L3 ........ (3) : wherein p is a coefficient of resistance of the conductive ink~ filled in the pumping tube 14, ~ is its inner width and H is it8 height.

:~ 15~ ~ Arranging the equation (1),(2),and (3), F can be expressed ~ ~a8 an quation:
,, :

F - ~3IB = L3 x L3 xB
P H

::
, :

2062~11 . .

L V
3 x B

H
L VH
3 xB
pL3 VH x B ..... - ( 4 ) Consequently the conductive material in the pumping tube 14 is accelerated by a force F calculated by the equation (4) in the pumping tube member 24 installed between the first and second magnet panel 20, 22.

Assuming that the density of the conductive material filled in the tube 14 is "d" and friction and viscosity resistance are negligible, the acceleration "a" of the conductive material caused by a force F is expressed as:

a= d~LB = dVLB ,,,,, (5) Assuming that the conductive material filled in the pumping tube 14 of the pumping tube member 24 is ink, the ink is ejected toward the exit of the tube 14 with an acceleration ~ determined by the equation (5).

Assuming that an initial speed of the ink ejected from the tube 14 of the pumping tube member 24 is "O"(zero), the amount of ink Q ejected for a time t at an acceleration determined by the equation ~5) is expressed as:

2062~

p= lat2= 2Bdt ,,..(6) Accordingly the conductive ink in the pumping tube 14 of height "H" and width "L3" is ejected by a force "F" and acceleration "a" determined in the equation (4) and (5) owing to a voltage "V" applied between the first and second electrode 16, 18 of the pumping tube 14. So it is proved that the amount of ink Q ejected with the force F and the acceleration (a) is controlled by adjusting the applied voltage V or the time t in the equation (6).

The ink is ejected from the tube and adhere to a printing paper (not shown in drawings) facing with the pumping tube 14, and an pictorial image is formed on the paper. The tone of the pictorial image formed on the paper is varied greatly by the ejected amount of ink Q.

For simplicity, assuming that the tone is proportional to the amount of ink, expression of tone of pictorial image is possible by changing the voltage applied to the first and second electrode 16, 18 and a time (t) of applied voltage V in the equation (6).

By applying a voltage V of square wave across the two electrodes 16, 18 of the pumping tube 14 of the pumping tube member 24 and changing the time (t), the amount of ink to be ejected can be controlled, the printed tone having a feature as shown in Fig.5A.

20`62~

Accordingly the tone of the pictorial image i8 related to time ~t) as shown in Fig.5A, if an input signal is applied to the two electrodes 16, 18 of the pumping tube 12 of the pumping tube member 24 after modulating the input signal by a method of pulse width modulation.

If the time of applying a voltage to the two electrodes 16, 18 is fixed and the voltage applied to the two electrodes 16, 18 is changed, a more linear feature of tone is obtained as shown in Fig.5B. For example, a linear feature of tone is produced as shown in Fig.5B, if a print input signal is applied to the two electrodes 16, 18 of the pumping tube 14 after modulating the print input signal by a method of pulse height modulation.

The acceleration a in the equation (5) does not count for loss factors such as viscosity of the ink filled in the tube 14, friction force between the ink and the inner wall of the tube 14, the gravity, an air resistance, etc. under the real situation.
Assuming the loss caused by these factors is f(v), the pumping acceleration Pa in the equation (5) needs to be modified as the following equation:

Pa = dH~3 ( v~HB_f (v) ) .. (7) wherein v represents speed.

The pumping acceleration Pa in fact should be considered in the relation between the ejected amount of ink Q and the applied ~062711 .

voltage V, or the ejected amount of ink Q and the time of ejection (t). An expert skilled in the art will be able to decide the pumping acceleration by experiment. Consequently the ink filled in the pumping tube 14 is ejected when the signal responding to a print signal is applied to the pumping tube 14 of the pumping tube member 24.

In this embodiment, a uniform magnetic field is applied to the pumping tube member by attaching a permanent magnet on the top and bottom side of the pumping tube member 24. However, the permanent magnet can be replaced by electromagnet made of such a coil winding.

In conclusion, the print head ejects conductive ink by the electromagnetic pumping and can express continuous tone by regulating an amount of ejected ink by modulating the print signal in an electromagnetic pumping drop-on-demand ink jet print head.

While the foregoing provides a full and complete disclosure of the preferred embodiments of the present invention, various modifications, alternate constructions and equivalents thereof may be employed without departing from the true spirit and scope of the invention. Therefore, the above description and illustration should not be construed as limiting the saope of the invention, which is defined by the appended claims.

Claims

1. An ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by an electromagnetic pumping principle, comprising:

a magnetic field generating means for generating a uniform magnetic field from a first space to a second space; and a pumping tube member comprising a plurality of pumping tubes having an isolated first and second electrode formed separately in a center of an insulation panel at regular intervals, being installed in a magnetic field, wherein said conductive ink is ejected from said pumping tube by applying a voltage to said first and second electrode.

2. The ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by the electromagnetic pumping as claimed in Claim 1, wherein said pumping tube of said pumping tube member is a quadrangle tube.

3. The ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by the electromagnetic pumping as claimed in Claim 2, wherein said first and second electrode of said pumping tube is of metal and coated on its right and left inner wall of said quadrangle tube.

4. The ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by an electromagnetic pumping principle, comprising:

a pumping tube member (24) incorporating a plurality of pumping tubes (14) having an isolated first electrode (16) and second electrode (18) and being formed separately at regular intervals in a center of an insulation panel (12)of given thickness and length; and a first magnet panel (20) and second magnet panel (22) installed on a top and bottom side of said pumping tube member (24) for applying a uniform magnetic field to said pumping tube member (24).

5. The ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by the electromagnetic pumping as claimed in Claim 4, wherein said insulation panel (12) is a glass or a silicon wafer.

6. The ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by the electromagnetic pumping as claimed in Claim 4 or Claim 5, wherein a shape of said pumping tube of said pumping tube member is a quadrangle tube.

7. The ink jet print head of electromagnetic pumping drop-on-demand type for ejecting conductive ink by the electromagnetic pumping as claimed in Claim 6, wherein said first and second electrode of said pumping tube is a metal and coated on an inner wall of right and left side of said quadrangle tube.

8. The ink jet print head of electromagnetic pumping drop-on-demand for ejecting a conductive ink by an electromagnetic pumping as claimed in Claim 4 or Claim 6, wherein said first and second magnetic panels (20) and (22) each have a magnetic pole of the South (S) and the North (N) and are arranged from a top to a bottom side around said insulation panel (12).

9. Each and every novel feature or novel combination of features herein disclosed.