EP1614545A1 - Pumping method with printing head - Google Patents

Abstract

The method involves the use of a printing head (11) with one or more liquid channels (14) with openings (15), whereby pressure is generated to act upon the liquid in order to eject drops (16) out of the respective openings. The pressure in each liquid channel is generated in an individually associated closed pressure chamber (20) and the liquid is subjected to the pressure from the pressure chamber. An independent claim is also included for an ink printing method.

Description

The invention relates to a pumping method with the features in the preamble of claim 1.

A pumping method of this kind is used, for example, in an ink printing method in which electrothermal ink jet printing heads are used and which operates on the bubble jet principle. The inkjet print head has a multiplicity of individual nozzles, from which individual droplets of defined size are produced under the action of an electronic, complex control and ejected in a defined pattern in the direction of a recording medium. In such ink printheads located in an ink-filled capillaries near the opening of this a heating element, which is designed as an electrical resistance. If a certain heat energy is supplied to this heating element by means of a short current pulse, extremely rapid heat transfer to the ink liquid first results in a rapidly expanding ink vapor bubble, which then relatively quickly collapses after the energy supply has been removed and cooled by the ink liquid. The pressure wave created by the vapor bubble inside the capillaries causes an ink droplet from the nozzle opening onto the surface of a Record carrier emerge. As can be seen, such electrothermal ink jet heads and the entire device are extremely complicated, expensive and expensive. For each individual ink channel associated with this heating element in the form of an electrical resistance with supply lines, associated control, etc. is required. If it is made clear that ink heads of the type described can have a large number of ink channels, it becomes clear how complex such a design with each ink channel own heating element.

The invention has for its object to design a method of the type mentioned above so that the cost is substantially reduced and facilities for this are extremely inexpensive to produce.

The object is achieved in a pumping method of the type mentioned according to the invention by the features in claim 1. Further advantageous features of the invention and embodiments will become apparent from the dependent claims. This method according to the invention has the advantage that for producing a liquid drop per liquid channel to the liquid contained therein exerted by the respective associated closed pressure chamber external pressure and thereby the liquid for ejecting a liquid drop can be pressurized directly with pressure. The individual pressure chambers can be pressurized in a particularly simple manner by stimulating a correspondingly adapted medium contained therein, for example, preferably with a high-energy beam, eg a laser beam, whereby gas bubbles are produced in the respective pressure chamber and an overpressure is thereby generated the pressure chamber closing the wall is pre-curved to generate pressure in each associated liquid channel to this and thereby exerted pressure on the liquid and a drop of liquid is ejected. The high energy beam is tuned to the medium in the pressure chambers. In the case of a laser beam used by the deflection of a variety be excited by pressure chambers along a row. Due to the intensity of the high-energy beam, the size of each ejected liquid drop per opening can be controlled. This pumping process is extremely simple. The construction effort is low. This reduces the costs considerably and leads to a very small footprint. It can be used in various technical fields, wherein the liquid may consist, for example, of ink, plastic, a pharmaceutical product or the like.

Advantageously, this method can be used e.g. as ink printing method with ink to be designed as a liquid, which is applied in at least one ink channel contained in a print head fluid for ejecting an ink drop from an associated pressure chamber with the pressure generated in the pressure chamber.

Further details and advantages of the invention will become apparent from the following description, which is referred to here to avoid repetition.

The full text of the claims is not reproduced above solely to avoid unnecessary repetition, but instead referred to merely by reference to the claims on it, which, however, all of these claims have to be considered as explicitly and essential to the invention here to apply. All features mentioned in the preceding and following description as well as the features which can be taken from the drawing alone are further constituents of the invention, even if they are not particularly emphasized and in particular not mentioned in the claims.

Fig. 1

eine schematische Draufsicht eines Teils einer Einrichtung mit einem thermischen Druckkopf,

Fig. 2

einen schematischen Schnitt entlang der Linie II - II des Druckkopfes in einer Phase,

Fig. 3

einen schematischen Schnitt entsprechend demjenigen in Fig. 2 während der Erzeugung eines Flüssigkeitstropfens.

The invention is explained in more detail with reference to an embodiment shown in the drawings. Show it:

Fig. 1

a schematic plan view of a portion of a device with a thermal printhead,

Fig. 2

a schematic section along the line II - II of the printhead in one phase,

Fig. 3

a schematic section corresponding to that in Fig. 2 during the generation of a liquid drop.

The invention is explained below using the example of the design as ink printing method with ink as liquid. However, it goes without saying that this pumping method can also be used in other technical fields in the same way and with the same advantages.

In the drawings, a device 10 is shown schematically with the only parts necessary to illustrate the invention, which consist of an ink jet print head 11 and a schematically indicated power generator 12 for generating heat energy. By means of this device 10, an ink printing method according to the so-called. Bubble jet principle is possible. The inkjet print head 11 has at least one, for example cuboidal body 13, which contains one or more individual ink channels 14 with end nozzle openings 15. The device 10, in particular the ink jet print head 11, is shown greatly enlarged. The individual ink channels 14 actually have, for example, a distance of only 50 μm from each other and are correspondingly narrow. As can be seen Fig. 1, the individual ink channels 14 are arranged side by side in the body 13 along a row, the body 13 may have a very large number of such ink channels 14 with nozzle openings 15, which may be 600 per inch or more. The body 13 may for example be formed of glass, in which case the individual ink channels 14 and / or nozzle openings 15 are formed in the body 13 by mechanical or chemical processes, eg by etching, in a particularly simple manner can. For ejecting ink drops 16 from the respective nozzle openings 15 of the ink channels 14, pressure is applied to the ink in the ink channels 14. This pressure is generated per ink channel 14 in at least one respectively associated closed pressure chamber 20, which is adjacent to a region of the respective ink channel 14. In the embodiment shown, a plurality of individual pressure chambers 20 are arranged side by side along a row, each of which is adjacent to and associated with a respective ink channel 14. The individual pressure chambers 20 are contained in at least one body 21, which, like the other body 13, can also be designed as a rectangular body, for example. The body 21 is for example made of glass or other material which is permeable to a high-energy beam explained later. In the design of the body 21 made of glass, the individual pressure chambers 20 can be produced in a particularly simple manner by mechanical or chemical methods, for example by etching. Both bodies 13 and 21 are preferably connected together to form a unit, wherein between two bodies 13 and 21, a wall 22 extends. The wall 22 is designed in particular as a membrane. It may be of particular advantage if this wall 22 of electrically conductive material, for example of metal, such as gold, beryllium od. Like. Is formed. Then, the wall 22 can be put on voltage and heated by electrical resistance heating with the advantage that then during this heating, both bodies 13 and 21 are pressed together and in this way can then be firmly and tightly connected.

As can be seen from the drawings, the ink channels 14 in the body 13 are approximately in the region of the respective associated pressure chambers 20 with the wall 22, which closes the respective pressure chamber 20 tight, in such contact that the wall 22 in this area directly on the ink can act in the respective ink channel 14.

The ink jet print head 11 is designed so that the pressure per ink channel 14 is generated in a respective associated closed pressure chamber 20 and the ink is then pressurized by the pressure chamber 20, wherein the pressure generated in the pressure chamber 20 via the wall 22 is exerted directly on the ink in the respective ink channel 14. The wall 22 is deformable at least insofar as it can bulge from the initial state shown in FIG. 2 at pressure increase in the pressure chamber 20 in Fig. 3 to the left towards the respective associated ink channel 14, thereby pressurizing the ink in the ink channel 14 and from the nozzle opening 15, a corresponding ink droplet 16 is pressed out.

Each closed by the wall 22 pressure chamber 20 is filled with a medium 23, which is heated so that thereby the wall 22 for generating pressure in the respective ink channel 14 according to FIG. 3 is bulged. The medium 23 can be varied, e.g. made of a solid material. It is particularly preferred if the medium 23 is made of a gaseous or, in particular, a liquid medium, e.g. Water, consists, with each pressure chamber 20 is filled. Upon introduction of heat, such a medium 23 is heated in such a way that gas bubbles 24 indicated in the respective pressure chamber 20 in FIG. 3 are formed and an overpressure is generated by which the wall 22 is bulged in the respective ink channel 14 to generate pressure. If the heating drops, the wall 22 returns at least to the starting position shown in FIG. This happens e.g. by own resilience, by pressure drop in the respective pressure chamber 20, e.g. Negative pressure, od. Like.

The heating of the medium 23 in the chamber 20 is done from the outside through the so far permeable body 21 through eg by means of a high energy beam, for example a laser beam generated by the power generator 12 and is directed in a corresponding manner to the respective desired pressure chamber 20. Due to the intensity of the respective high-energy beam, the size of the respectively ejected ink drops 16 per ink channel 14 can be controlled. The device 10 has in the body 13, for example, a plurality of individual ink channels 14 with Nozzle openings 15 and in the body 21 z. B. a plurality of associated pressure chambers 20, all of which, for example, along a row are arranged side by side, as is apparent from Fig. 1. The emitted from the power generator 12 high-energy beam is controlled accordingly, wherein the individual pressure chambers 20 are excited accordingly by the high-energy beam.

The formation of the body 13 and 21 as a glass body has the advantage that the ink channels 14 formed therein with nozzle openings 15 and pressure chambers 20 in a particularly simple manner and also very accurately by mechanical or chemical methods, eg by etching, can be produced. It is also advantageous that passes through a thus designed glass body 21 of the high energy beam, which is emitted from the outside of the power generator 12 passes through the body 21 into the region of the pressure chamber 20, and this od virtually without losses, scattering. Like. Will Ink channels 14 such ink supplied, which is curable by means of UV light, then the material of the wall 22 is then advantageously chosen such that is impermeable to the high energy beam of the power generator 12 to prevent drying out of the ink. The particular advantage of the device 10 is that it is extremely simple compared to complex, complicated and expensive electronic devices. Also, as compared with known electrothermal ink-jet heads in which the ink per ink channel is imparted thereto by generating pressure waves formed by heating the ink by means of an electrical resistance, the device 10 according to the invention is particularly simple, it will be understood that FIG Such an electro-thermal ink jet heads for each ink channel an associated own heating element in the form of an electrical resistance with cables, associated control, etc. is necessary. In comparison, the device 10 according to the invention requires only the power generator 12 and the control of the high energy beam for scanning the individual pressure chambers 20 to produce ink droplets 16 and thus a printed image. wherein by varying the intensity of the high energy beam, the respective size of the ink drops 16 can be varied accordingly.

Claims (18)

Pumping apparatus comprising a printhead (11) having one or more fluid channels (14) having openings (15) for generating pressure on the liquid to expel drops (16) from the respective openings (15),
characterized,
that the pressure of each liquid channel (14) is generated in a respectively associated closed pressure chamber (20) and the liquid is acted upon by the pressure chamber (20) with pressure. Method according to claim 1,
characterized,
in that the pressure generated in the pressure chamber (20) is exerted directly on the liquid via a deformable wall (22) terminating the pressure chamber (20). Method according to claim 1 or 2,
characterized,
in that each closed pressure chamber (20) is filled with a medium (23) which is excited, eg heated, in such a way that the wall (22) for pressure generation in the respective liquid channel (14) is thereby bulged toward it. Method according to claim 3,
characterized,
that each closed pressure chamber (20) is filled with a gaseous or in particular liquid medium (23), eg with water, which is excited, eg heated, in such a way that gas bubbles (24) thereby form in the respective pressure chamber (20) and As a result, an overpressure is generated by which the wall (22) is pre-curved to generate pressure in the respective fluid channel (14) towards this. Method according to claim 3 or 4,
characterized,
that when the excitation, for example the heating, of the medium (23) in the pressure chamber (20) decreases, the wall (22) returns to at least the initial position, eg by its own resilience, by a pressure drop in the respective pressure chamber (20) , eg negative pressure, or the like. Method according to one of claims 3 to 5,
characterized,
that the respective pressure chamber (20) is excited by means of a high-energy beam, for example a laser beam. Method according to claim 6,
characterized,
that is each port (15) controlled by the intensity of the high energy beam, the size of each ejected drop (16). Method according to claim 6 or 7,
characterized,
that a plurality of individual, each with a fluid channel (14) associated pressure chambers (20) is arranged along a row next to one another and is excited by the high energy beam targeted. Method according to one of claims 1 to 8,
characterized,
in that the individual pressure chambers (20) are contained in at least one body (21) which is permeable at least in the area of the pressure chambers (20) for the high-energy beam, eg laser beam. Method according to claim 9,
characterized,
in that the at least one body (21) is formed from glass. Ink printing method according to one of claims 9 or 10,
characterized,
that the individual pressure chambers (20) are formed by mechanical or chemical processes, for example by etching, the body (21). An ink printing method according to any one of claims 1 to 11,
characterized,
in that at least one fluid channel (14) with end-side opening (15) is formed in at least one body (13), each fluid channel (14) being approximately in the region of the respective associated pressure chamber (20) with the wall (22) containing the pressure chamber (15). 20) is in contact, such that the wall (22) can act directly on the liquid. Method according to claim 12,
characterized,
in that the at least one body (13) is formed from glass. Method according to claim 12 or 13,
characterized,
that the individual liquid passages (14) and / or openings (15) are formed by mechanical or chemical processes, for example by etching, the body (13). Method according to one of claims 12 to 14,
characterized,
in that the at least one body (13) is connected to the other body (21) containing the individual pressure chambers (20), the wall (22) extending between both bodies (13, 21). Method according to one of claims 2 to 15,
characterized,
that the wall (22) is formed as a membrane. Method according to one of claims 2 to 16,
characterized,
in that the wall (22) is made of electrically conductive material, eg gold, beryllium or the like, and both bodies (13, 21) are connected by compression during electric resistance heating of the wall (22). Method according to one of claims 1 to 17,
marked by
the design as an ink printing method, wherein in at least one in the print head (11) contained liquid channel (14) located ink for ejecting an ink droplet (16) of a respectively associated Pressure chamber (20) is acted upon by the pressure generated in the pressure chamber (20).

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