Nozzle Device For Ink Jet Printing Equipments

Abstract

A nozzle device for ink jet printing equipments having a tube whose open end constitutes an ink nozzle exit wherein there is provided a protective member in which there is formed an extremely narrow slit extending horizontally inward from its end face, said slitted member being fitted around the periphery of the tube with the nozzle portion thereof exposed so as to allow the ink excessively flowing out of the exit end of the nozzle to be sucked into the slit by the capillary suction afforded thereby.

Description

This invention relates to a nozzle device for ink jet printing equipments. An ink jet printing equipment known to date comprises a nozzle device consisting of a narrow tube into which there is supplied ink at a pressure and suction means which draws ink out of the nozzle by means of an electrical field, magnetic field or supersonic waves and jets the ink in very fine particles on to a medium of recording. The prior art ink nozzle device consists, as shown in FIGS. 1A to 1D, of an extremely narrow tube 11, 0.15 mm in outer diameter whose open forward end constitutes a nozzle outlet through which to jet ink, and a protective member 10 surrounding said narrow fragile tube. Into this tube is supplied ink 21 at a hydrostatic pressure. As illustrated in FIG. 1A, there is presented the meniscus 22 of ink at the forward end of the tube 11 corresponding to an equilibrium between the hydrostatic pressure prevailing inside the nozzle and the surface pressure of the ink 21. When the ink is subjected to a suction acting in the forward direction of the nozzle where there is formed such meniscus, then the meniscus is deformed and finally broken to pieces, so that the ink is ejected in very fine particles.

However, external vibrations imparted to the nozzle or unduly high hydrostatic pressure applied to the ink sometimes prevents it from forming the desired meniscus indicated by the curve 22 of FIG. 1A. In such case, ink runs over even the peripheral surface of the tube 11 and is collected thereon as illustrated by the curve 23 of FIG. 1B. In extreme cases, the ink is deposited, as shown by the curves 24 and 25 of FIGS. 1C and 1D, on not only the peripheral surface of the tube 11 but also the forward end face 13 of the protective member 12. Under such conditions, the ink does not form the desired meniscus, failing to be ejected properly in uniform particles. Particularly in the cases of FIGS. 1C and 1D, the ink can not be jetted at all. With the conventional ink jet printing equipment, therefore, it was necessary to take out the nozzle for washing each time the ink fails to jet freely.

It is accordingly the object of this invention to provide an ink nozzle device wherein, in case ink unduly runs over the peripheral surface of the nozzle, such excess deposition can be naturally removed by the capillary suction afforded by the very narrow slit formed in the neighboring member, thereby enabling the ink always to present the desired meniscus and be ejected in uniform particles under a stable condition.

According to the present invention this object is attained by providing an ink sucking slit extending in the neighborhood of the peripheral surface of the opposite side of the nozzle to its exit end.

Therefore, the ink nozzle device according to the invention provides an ink jet printing equipment which performs printing under very stable conditions against, for example, external vibrations and eliminates the necessity of carrying out a time-consuming operation of frequently taking out the nozzle for washing in order to remove ink attached to the periphery thereof.

The present invention can be more fully understood from the following detailed description when taken in conjunction with reference to the appended drawings, in which:

FIGS. 1A to 1D are sectional views of the nozzle device, showing the various forms of ink occurring during operation; FIGS. 2 to 4 are perspective views of the nozzle devices according to the embodiments of the invention;

FIG. 5 is a perspective view, partly in section, of a nozzle device according to another embodiment of the invention; and

FIG. 6 represents the case where an ink nozzle device according to the embodiment of FIG. 3 is put to practical application.

FIG. 2 represents a first embodiment of this invention. A tube 11 whose open forward end constitutes the exit end of an ink nozzle cosists, for example, of an extremely narrow glass tube about 0.1 to 0.12 mm in inner diameter and 0.135 to 0.155 mm in outer diameter. This glass tube 11 is surrounded for protection by a protective member 12 consisting of a round metal rod so as to have its open forward end project to the outside about 0.5 mm. The protective member 12 has an elongated ink sucking slit 31 about 0.15 mm wide extending horizontally inward from its end face 13 in a manner to divide the protective member 12 into two parts. Said slit 31 protects the tube 11 by holding it therein. Accordingly, the ink excessively flowing out of the open forward end of the tube and deposited on the peripheral surface of the tube 11 up to the forward end face 13 of the protective member 12 is immediately drawn or sucked into the metal walled slit 31 by the capillary suction afforded thereby. It is further preferred to coat a water-repellent material on the peripheral surface of the exposed portion of the tube 11 so as to prevent ink from continuously settling thereon. This holds true with the following embodiments.

FIG. 3 illustrates a nozzle device according to another embodiment of the invention. As in FIG. 2, the tube 11 is formed of an extremely narrow glass tube, which is inserted into a protective member consisting of a round metal rod so as to have its forward end project to the outside about 0.5 mm. This protective member 12 has four elongated ink sucking slits 32 about 0.15 mm wide formed in the peripheral surface so as to extend horizontally lengthwise from the forward end face 13 of said member 12, with the bottom of each slit 32 disposed near the peripheral surface of at least that part of the tube which faces the forward end surface of said protective member 12. The embodiment of FIG. 3 is characterized in that the protective member 12 has a greater mechanical strength than that of FIG. 2.

FIG. 4 indicates a nozzle device according to still another embodiment of the invention. This embodiment has a plurality of juxtaposed tubes 111 to 113, which are each formed of a glass tube as in FIG. 2 and inserted into a protective member 14 consisting of a metal plate so as to have the forward end project to the outside about 0.5 mm from said metal plate. An ink nozzle device provided with such plural tubes is used with a recorder which records a plurality of letters at the same time. Said metal plate 14 includes ink drawing or sucking slits 331 to 333 whose bottom is disposed near the periphery of said tubes 111 to 113, a guide groove 34 communicating with all these slits 331 to 333, and an ink holding cavity 35 in which there is contained a spongy material 36. The ink excessively running out of the open forward end of the tubes 111 to 113 is sucked into the corresponding slits 331 to 333 and then conducted through the guide groove 34 to the ink holding cavity 35 where the ink is absorbed into the spongy material.

FIG. 5 shows a nozzle device according to a further embodiment of the invention. A tube 16 whose open forward end constitutes the exit end of an ink nozzle consists of a tapered glass tube whose forward end is as narrow as 0.1 to 0.12 mm in inner diameter and 0.135 to 0.155 mm in outer diameter and which grows progressively thicker toward the rear end. Said glass tube 16 is held in the central part of a through hole 37 about 0.5 mm in diameter bored in a metal plate 17 so as to have its forward end project to the outside about 0.5 mm from said metal plate 17. To the backside of the metal plate 17 is tightly attached, for example, a spongy material 38 to allow the tube 16 to be inserted therethrough. The ink flowing out of the open forward end of the tube 16 is sucked into a groove defined by the outer peripheral wall of the tube 16 with the inner wall of the through hole 37 of the metal plate 17 and conducted to an ink absorber disposed behind the metal plate 17 and formed of a spongy material 38.

FIG. 6 represents the case where an ink nozzle device according to the embodiment of FIG. 3 is put to practical application. An ink nozzle device consisting of a tube 11 having an open forward end acting as a nozzle exit end and a protective member provided with ink sucking slits 32 is inserted into a nozzle holder 52. The ink sucking slits 32 extend lengthwise of the protective member 12 up to an ink absorbing member fitted to the rear end of the nozzle holder 52 and formed of, for example, a spongy material 53. To the forward end of the nozzle holder 52 is attached a metal nozzle plate 51. The ink nozzle device illustrated in FIG. 6 is used with an ink jet printing equipment which ejects ink using a electrostatic field. Said nozzle plate 51 is intended to elevate the action of an electrical field generated ahead of the tube 11. To the rear end of the tube 11 is fitted an ink supply pipe 54. The ink running out of the nozzle is immediately drawn or sucked into the slits 32 and conducted therethrough rearward of the nozzle holder 52 by the capillary suction afforded by said slits 32 up to the ink absorbing member 53 where the ink is preserved.

In the embodiments of the present invention described above, electrostatic pressure is impressed on the ink to let the ink be kept in the desired meniscus when it is jetted out of the nozzle front so that a high potential difference is created between the ink kept in such meniscus and an electrode disposed apart from the nozzle front end, thereby generating electrostatic attraction so that ink droplets of the ink having the desired meniscus are jetted to produce printing letters and the like on the recording medium.

While only several embodiments of the present invention have been shown and described it will be obvious to those persons of ordinary skill in the art that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A nozzle device for ink jet printing equip-ment comprising:

a nozzle tube for jetting out ink droplets; and

a protective member disposed about the length of said nozzle tube and leaving an exposed discharge tip of said nozzle tube, said protective member having at least one capillary peripheral slit extending from the end near the discharge tip of said nozzle tube to a rearward portion near the other end of said protective member so that excessive ink collecting at the discharge tip of said nozzle tube will be drawn by capillary action through said at least one capillary peripheral slit away from the exposed discharge tip.

2. A nozzle device for ink jet printing equipment comprising:

at least one nozzle tube for jetting out ink droplets; and

a substantially planar member having at least one aperture through which said at least one nozzle tube is concentrically disposed so as to exit on one side thereof, said at least one nozzle tube positioned therein to leave a capillary cylindrical space that is interposed between said at least one aperture and said at least one nozzle tube so that excessive ink collecting at the discharge tip of said at least one nozzle tube will be drawn by the capillary action away from the discharge tip.

3. A nozzle device for ink jet printing equipment comprising:

a nozzle tube for jetting out ink droplets;

a cylindrically-shaped protective member concentrically disposed about the outside periphery of said nozzle tube and leaving an exposed discharge tip, said protective member having at least one capillary peripheral slit extending from the forward face near the discharge tip of said nozzle tube rearward to near the other end of said protective member;

a substantially cylindrically-shaped support member positioned about and exposing a portion of said protective member and having an aperture disposed concentrically therethrough, said aperture of approximately complimentary diameter to said protective member so as to receive the outside periphery thereof; and

a cylindrical nozzle plate of smaller diameter than said support member and extending therefrom, and concentrically positioned about the exposed portion of said protective member, said nozzle plate having a centrally disposed aperture substantially complimentary with the outer periphery of said protective member so that as ink is ejected through the discharge tip of said at least one nozzle tube any excess ink will contact and be drawn through said at least one capillary peripheral slit by the capillary action thereof.

4. The nozzle device as in claim 2 wherein disposed about said other end of said protective member is a sponge communicating with a portion of said at least one capillary peripheral slit to absorb the ink that is drawn therethrough.