Jet print head

Details Jet print head Jet print head

1992-10-20

1995-03-28

Fuller, Benjamin R.

Incremental printing of symbolic information

Ink jet

Ejector mechanism

B41J 206

Patent

active

054021634

DESCRIPTION:

BRIEF SUMMARY
FIELD OF INVENTION

The invention relates to printing devices, and particularly, to a jet print head for such devices.


PRIOR ART

Known in the prior art is a print head supplying electro-conductive ink onto an information carrier by virtue of electro-dynamic force, comprising an ink chamber with an ink discharge port, having a plurality of parallel tubes of sufficiently large diameter which represent essentially capillary orifices. Each orifice has a pair of electrodes entering the orifice from the diametrically opposite sides of the tube, perpendicular to its axis. The head is embraced by a permanent horse-shoe magnet arranged so that all openings are permeable to a magnetic field created by the magnet (see U.S. Pat. No. 4,023,180). Current is passed through electricity conductive ink and interacts with the magnetic field of the permanent magnet once an electrical signal pulse is applied to the pair of electrodes. As a result, electro-magnetic force is developed, causing a drop of ink to be emitted from the capillary tube. The construction design of such a print head is quite complex because it requires the electrodes to be inserted into the capillary tubes and strict orientation of them in relation to the capillary tubes axes. Violation of this strict orientation is responsible for poor quality of printing. Apart from that, no sound connection of electrodes with electro-conductive bars is, in fact, possible. And, finally, to ensure reliable discharge of ink drops from the head orifice, every capillary tube should operate in equal conditions, i.e. the magnetic field in the zone of electrodes should be the same, and equally the same should be the force of an electrical signal pulse passing through them. When a horse-shoe magnet is used, the magnetic field in the center will be substantially weaker than on the periphery, which fact tells substantially the quality of printing because it affects the formation of ink drops discharged from the capillary tube. It will be noted in the meanwhile that to create an essentially homogenous field throughout the whole print head surface, the horse-shoe magnet must be many times larger than the area covered by the capillary tubes.
Known in the prior art is a jet print head comprising a chamber for electro-conductive ink equipped with an ink discharge port to express ink onto the information carrier. The ink discharge port comprises a multilaminate structure formed on an underlay with a group array of parallel rows of orifices made in the same structure in the form of capillary openings communicating with the inside chamber storage. Each given row of orifices has an electrode of the same polarity which is common for this row, and every orifice of this group has an individual electrode of opposite polarity, and all the electrodes are placed on one and the same side of the underlay facing the chamber in the same plane directed perpendicular to the axis of orifices, and make one layer of the multilaminate structure. The electrodes of different rows are electrically isolated from each other. This discharge port also has electro-conductive bars of individual electrodes which exist in the plane parallel to that of electrodes, and are separated from them by the dielectric layer, oriented or patterned on the lines criss-crossing the other lines which connect the individual electrodes of each group at a 90 degree angle, and joined to the individual electrodes of relevant groups by crosspieces passing through the dielectric layer. The permanent magnet of such head is represented by the magnetic layer disposed on the underlay parallel to the plane of the electrode groups from the side opposite to ink or colour liquid.
The structure of this head reveals a number of useful results, for example, in simplification of its design due to the reduced number of electric current feeders (just one bar for a row of orifices), and also in higher quality of printing owing to greater reliability of expressing drops from the orifices due to uniform field stress exerted by the magnetic layer. Apar

REFERENCES:
patent: 4023180 (1977-05-01), Zenner
patent: 4057807 (1977-11-01), Fischbeck et al.

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